ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Articles  (150)
  • kriging  (91)
  • groundwater  (62)
  • Springer  (150)
  • Geosciences  (137)
  • Architecture, Civil Engineering, Surveying  (22)
  • 1
    Electronic Resource
    Electronic Resource
    Micro-scale modelling in the study of plume evolution in heterogeneous media (1987)
    Springer
    Stochastic environmental research and risk assessment 1 (1987), S. 263-279 
    Details
    ISSN: 1436-3259
    Keywords: Porous media ; heterogeneity ; groundwater ; dispersion ; stochastic theory ; plume evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The migration of contaminants in heterogeneous aquifers involves dispersive processes that act at different scales. The interaction of these processes as a plume evolves can be studied by micro-scale modelling whereby two scales, a local- or micro-scale and an aquifer- or macro-scale, are covered simultaneously. Local-scale dispersive processes are represented through the local dispersion coefficient in the transport equation, while large-scale dispersion due to heterogeneities is represented through the resolution of the flow field and the diffusive exchange between streamtubes. The micro-scale model provides both the high degree of resolution compatible with local-scale processes, and the extent required for the approach to asymptotic conditions, using grids of up to a million nodal points. The model is based on the dual potential-streamfunction formulation for flow, and the transport problem is formulated in a natural coordinate system provided by the flownet. Simulations can be used to verify stochastic theories of dispersion, without the restrictive assumptions inherent in the theory. For the two-dimensional case, results indicate convergence of the effective dispersivity to the theoretical macrodispersivity value. Convergence takes place within a travel distance of about 50 correlation lengths of the hydraulic conductivity field. However, the approach taken to asymptotic conditions, as well as the macrodispersivity value, may differ for different realizations of the same medium. The influence of early-time events such as plume splitting on the asymptotic convergence remains to be investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01543098
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Analytical expressions of conditional mean, covariance, and sample functions in geostatistics (1996)
    Springer
    Stochastic environmental research and risk assessment 10 (1996), S. 279-294 
    Details
    ISSN: 1436-3259
    Keywords: Linear estimation ; interpolation ; kriging ; splines ; conditional
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract This work presents analytical expressions for the best estimate, conditional covariance function, and conditional realizations of a function from sparse observations. In contrast to the prevalent approach in kriging where the best estimates at every point are determined from the solution of a system of linear equations, the best-estimate function can be represented analytically in terms of basis functions, whose number depends on the observations. This approach is computationally superior when graphing a function estimate and is also valuable in understanding what the solution should look like. For example, one can immediately see that all “singularities” in the best-estimate function are at observation points.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581870
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Simulation of normal distributed smooth fields by Karhunen-Loéve expansion in combination with kriging (1997)
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 459-482 
    Details
    ISSN: 1436-3259
    Keywords: Karhunen-Loéve expansion ; Empirical Orthogonal Functions ; stochastic simulation ; gaussian fields ; analytical covariance functions ; eigenfunctions ; kriging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Simulation of multigaussian stochastic fields can be made after a Karhunen-Loéve expansion of a given covariance function. This method is also called simulation by Empirical Orthogonal Functions. The simulations are made by drawing stochastic coefficients from a random generator. These numbers are multiplied with eigenfunctions and eigenvalues derived from the predefined covariance model. The number of eigenfunctions necessary to reproduce the stochastic process within a predefined variance error, turns out to be a cardinal question. Some ordinary analytical covariance functions are used to evaluate how quickly the series of eigenfunctions can be truncated. This analysis demonstrates extremely quick convergence to 99.5% of total variance for the 2nd order exponential (‘gaussian’) covariance function, while the opposite is true for the 1st order exponential covariance function. Due to these convergence characteristics, the Karhunen-Loéve method is most suitable for simulating smooth fields with ‘gaussian’ shaped covariance functions. Practical applications of Karhunen-Loéve simulations can be improved by spatial interpolation of the eigenfunctions. In this paper, we suggest interpolation by kriging and limits for reproduction of the predefined covariance functions are evaluated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02428429
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Generation of runoff series at ungauged locations using empirical orthogonal functions in combination with kriging (1992)
    Springer
    Stochastic environmental research and risk assessment 6 (1992), S. 255-269 
    Details
    ISSN: 1436-3259
    Keywords: Emprical Orthogonal Functions ; interpolating runoff ; kriging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The method of Empirical Orthogonal Functions (EOF method) is combined with an objective interpolation technique, kriging, to generate runoff series at ungauged locations. In a case study the results are compared to series interpolated by a combination of EOF analysis and regression using catchment characteristics as independent variables. The results are also compared to linear weighting of an existing runoff series, a commonly used method for spatial interpolation. The influence of altitude on the runoff is studied comparing kriging based on 2 and 3 coordinates. The study showed that the capacity of EOF analysis combined with kriging is as good as the traditionally used linear weighting. The results, when altitude is included in the kriging, are improved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581620
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Determination of hydraulic diffusivity of aquifers by spectral analysis (1999)
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 85-99 
    Details
    ISSN: 1436-3259
    Keywords: Key words: Hydraulic diffusivity ; groundwater ; spectral analysis ; stochastic boundaries.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract: This study uses the cyclical frequency to develop the mathematical relationship between hydraulic diffusivity and spectral density functions calculated from groundwater level variation. Such relationship can be applied to (1) unsteady state, one-dimensional confined aquifer with time-dependent water level on both end boundaries, and (2) linearized unconfined aquifer with or without vertical recharge. The spectral density functions of groundwater fluctuations are largely affected by the spectral density functions obtained from time-dependent end boundaries and their cross-spectral density functions. Hydraulic diffusivity of an aquifer can be solved by type-curve matching technique at a specified frequency band under the conditions of (1) confined aquifer having equal time-dependent boundaries on both ends, (2) unconfined aquifer having equal time-dependent boundaries on both ends with surface recharge, and (3) unconfined aquifer subjected to surface recharge but neglecting the water table fluctuations on both end boundaries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004770050033
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Spatial rainfall estimation by linear and non-linear co-kriging of radar-rainfall and raingage data (1989)
    Springer
    Stochastic environmental research and risk assessment 3 (1989), S. 51-67 
    Details
    ISSN: 1436-3259
    Keywords: Spatial rainfall estimation ; kriging ; ordinary co-kriging ; disjunctive co-kriging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The feasibility of linear and nonlinear geostatistical estimation techniques for optimal merging of rainfall data from raingage and radar observations is investigated in this study by use of controlled numerical experiments. Synthetic radar and raingage data are generated with their hypothetical error structures that explicitly account for sampling characteristics of the two sensors. Numerically simulated rainfall fields considered to be ground-truth fields on 4×4 km grids are used in the generation of radar and raingage observations. Ground-truth rainfall fields consist of generated rainfall fields with various climatic characteristics that preserve the space-time covariance function of rainfall events in extratropical cyclonic storms. Optimal mean areal precipitation estimates are obtained based on the minimum variance, unbiased property of kriging techniques under the second order homogeneity assumption of rainfall fields. The evaluation of estimated rainfall fields is done based on the refinement of spatial predictability over what would be provided from each sensor individually. Attention is mainly given to removal of measurement error and bias that are synthetically introduced to radar measurements. The influence of raingage network density on estimated rainfall fields is also examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01543427
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Spatial variability and interpolation of daily precipitation amount (1992)
    Springer
    Stochastic environmental research and risk assessment 6 (1992), S. 209-221 
    Details
    ISSN: 1436-3259
    Keywords: geostatistics ; precipitation ; water balance models ; semivariogram ; kriging ; spatial variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Daily precipitation amounts show spatial variation over sub-continential regions. Point measurements, representative for regions of land, have to be interpolated towards unobserved locations. In this study four days in 1984 were selected to investigate the spatial variability of daily precipitation amount in North-western Europe in relation to the meteorological conditions. Data were interpolated using Kriging. Crossvalidation was used to compare interpolated values with measured values. Large differences in the spatial structure of daily precipitation amount are obsered as a result of different meterological conditions. Stratification of the study area into a coastal, a mountainous and an interior stratum proved to be successful, reducing the Mean Squared Error of Prediction with up to 55%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581451
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Spatial variability and interpolation of daily precipitation amount (1992)
    Springer
    Stochastic environmental research and risk assessment 6 (1992), S. 304-320 
    Details
    ISSN: 1436-3259
    Keywords: geostatistics ; precipitation ; water balance models ; semivariogram ; kriging ; spatial variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Daily precipitation amounts show spatial variation over sub-continential regions. Point measurements, represntative for regions of land, have to be interpolated towards unobserved locations. In this study four days in 1984 were selected to investigate the spatial variability of daily precipitation amount in north-western Europe in relation to the meteorological conditions. Data were interpolated using kriging. Crossvalidation was used to compare interpolated values with measured values. Large differences in the spatial structure of daily precipitation amount are observed as a result of different meteorological conditions. Stratification of the study area into a coast, a mountain and an interior stratum proved to be successful, reducing the Mean Squared Error of Prediction with up to 55%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581623
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Groundwater exploration using integrated geophysical techniques (1994)
    Springer
    Surveys in geophysics 15 (1994), S. 331-361 
    Details
    ISSN: 1573-0956
    Keywords: groundwater ; geophysics ; DC resistivity ; electromagnetics ; nuclear magnetic resonance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The integrated approach to solving complicated geological, hydrological and environmental problems is now widely used in geophysics. Among all the geophysical methods, electrical and electromagnetic techniques are the most popular in groundwater exploration due to the close relationship between electrical conductivity and some hydrogeological properties of the aquifer (e.g. porosity, clay content, mineralization of the groundwater and degree of water saturation). Case histories presented here show that by proper combination of different techniques such as conventional direct current (DC) resistivity as well as the more advanced electromagnetic (EM) methods and the most recent nuclear magnetic resonance (NMR) tomography, the reliability of interpretation as compared to that typical for the individual methods can be significantly improved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00665814
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Short-term and intermediate-term geochemical precursors (1988)
    Springer
    Pure and applied geophysics 126 (1988), S. 267-278 
    Details
    ISSN: 1420-9136
    Keywords: Earthquake prediction ; radon ; groundwater ; geochemical precursor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Detection of precursory phenomena in observation data is essential to earthquake prediction studies. Continuous monitoring of radon concentration in groundwater in Japan in one case showed a short-term anomaly related to a nearby earthquake. With the exception of the 1978 Izu-Oshimakinkai earthquake (M7.0), however, no abnormal change has been noted. This may be due partially to difficulty in detecting insignificant precursory signals from observation data, which ordinarily contains a noise-induced fluctuations, and partially to lack of understanding of the mechanism controlling the appearance of precursory phenomena. In order to increase our knowledge of the variation pattern of precursory changes in radon concentration of groundwater, hydrologic precursors with significant features are examined in this paper. Complexity of appearance of precursory phenomena and problems in assignment of the specific earthquake are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00878999
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 11
    Electronic Resource
    Electronic Resource
    Hydrogeologic role in sinkhole development in the desert of Kuwait (1994)
    Springer
    Environmental geology 23 (1994), S. 201-208 
    Details
    ISSN: 1432-0495
    Keywords: Sinkhole ; Desert ; groundwater ; urbanization ; Kuwait Desert ; Land subsidence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Sinkhole development is unlikely in desert areas with very low precipitation. However, a few cases of land subsidence and sinkhole development took place within the suburbs of Kuwait City. A few sinkholes developed in a sudden and rapid way, leading to great economic losses. In this paper the mechanism and causes of such a land subsidence are described. Decline in groundwater level and downward infiltration of excess irrigation are suggested to be the main factors in the development of the land subsidence in Kuwait. Urbanization and excessive garden irrigation are most probably the triggers of the sudden and rapid land subsidence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00771789
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    Characterization of groundwater flow in the Bailin hazardous waste-disposal site (Huesca, Spain) (2000)
    Springer
    Environmental geology 40 (2000), S. 216-222 
    Details
    ISSN: 1432-0495
    Keywords: Keywords contamination ; groundwater ; lindane ; waste disposal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  A serious problem in Spain is presented, where the water and soil were contaminated by lindane produced by the chemical industry, at a time when environmental legislation was limited, and the hydrogeological characterization of the low permeability materials was insufficient. The waste-disposal sites where the lindane accumulated lacked suitable sealing and also had notable filtration. The non-existence of a safe waste-disposal site, and the economic and social problems of transporting lindane residues forced the alternative proposal of confining these residues in situ (Government of Aragón, 1995, 1996). Once the surface sealing was carried out, the problem centred on the site's underground confinement. The purpose of this publication is to present the particular hydrogeological behaviour of materials, which were initially considered impermeable because of the presence of very consolidated sandstone beddings and the vertical disposition of the strata, and so allowed the lindane to escape through the groundwater. In addition, this publication describes the procedures carried out in order to achieve effective underground confinement at the waste-disposal site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002540000154
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    Electronic Resource
    Electronic Resource
    Pb on groundwater particles, Door County, Wisconsin (1994)
    Springer
    Environmental geology 24 (1994), S. 150-156 
    Details
    ISSN: 1432-0495
    Keywords: Pb ; groundwater ; particles ; Fe oxyhydroxides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Pb was detected on groundwater particles larger than 0.45μm. Pb concentration (micrograms per liter) showed positive correlations with particle concentration (milligrams per liter) at five sampled wells, although the slopes of the best-fit lines were different. X-ray fluorescence scans suggested that the particles primarily consist of K-Al silicate minerals, and that Pb is absorbed onto Fe oxyhydroxide coatings on Mg-rich silicates. Particle compositions varied at wells, but remained consistent at each well through the sampling period of a month. The particulate nature of Pb in groundwater could cause the spatial and temporal variations due to: (1) the unique composition of particles at wells, (2) the irregular pathways for groundwater particles, (3) the unpredictable amount of Pb-carrying particles entering the groundwater system during recharge events, and (4) the irregular sampling of groundwater particles subsequently dispersed along the advective flow path.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00767889
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 14
    Electronic Resource
    Electronic Resource
    Redox Processes in Groundwater Impacted by Landfill Leachate (1998)
    Springer
    Aquatic geochemistry 4 (1998), S. 253-272 
    Details
    ISSN: 1573-1421
    Keywords: Inorganic tracers ; dilution factor ; leachate attenuation ; redox zones ; groundwater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Groundwater downgradient from Trandum municipallandfill was investigated in summer 1996, with a viewto assessing the distribution of redox-sensitivespecies. The water table at Trandum is 10–26 metersbelow the surface. Monitoring well filters have beeninstalled at depths of up to 15 m below water table,covering an area of 400 m by 200 m. Groundwaterinfluenced by the landfill seems to be confined tothis area. Pristine groundwater has a chemicalsignature indicative of calcite and pyrite weathering.Groundwater influenced by leachate from the landfillexhibits an excess of alkalinity relative to calcium,which is likely to be derived from degradation oforganic matter in the landfill. Groundwaterimmediately below and downstream of the landfillcontains elevated concentrations of Fe and Mn, largelymobilized under reducing conditions from the aquifermatrix and reflected in depleted HNO3-extractable Feand Mn in sediment samples from the same area.Groundwater samples allow the tentative identificationof redox zones based on oxidized and reduced forms ofFe, Mn, N and S. A methanogenic zone is notobserved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009623205558
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 15
    Electronic Resource
    Electronic Resource
    Modelling of uranium and neptunium chemistry in a deep rock environment (1996)
    Springer
    Aquatic geochemistry 2 (1996), S. 345-358 
    Details
    ISSN: 1573-1421
    Keywords: bentonite ; groundwater ; uranium ; neptunium ; PHREEQE ; speciation ; geochemical modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract According to the present concept for final storage of spent nuclear fuel in Sweden, the spent fuel, encapsulated in copper or copper/steel canisters, will be placed in tunnels in a deep rock formation. The canisters will be surrounded by compacted bentonite clay acting as a buffer material. In connection with a safety analysis of such a storage facility, the total solubility of certain elements (e.g., uranium) as well as the transport properties (e.g., retardation due to sorption on mineral surfaces) of the long-lived radionuclides released from the canister have to be predicted or measured. The chemical conditions, governing the solubility and speciation of trace elements encountered in and around the repository depend on interactions between the ground water and the engineering materials in the repository and a production of oxidants due to radiolysis in the spent fuel. In the present study the speciation and solubility of uranium and neptunium in a bentonite-ground water system and in ground waters with compositions measured at a site at äspö, SE Sweden, have been calculated. The calculations have been carried out using a recent version of the geochemical computer code PHREEQE and the database HATCHES 5.0. Predictions of the uranium and neptunium concentrations in the ground water in the vicinity of a damaged high level waste repository have also been performed. The uranium concentration in the water in the bentonite barrier is predicted to be of the same order of magnitude or lower than that found in some granitic ground waters. For neptunium the calculations are uncertain due to the small amount of experimentally determined thermodynamic data and few verifications under the conditions (pH - Eh - carbonate concentration) considered. The predicted concentrations (ca 10−12 m, corresponds to ca 0.006 Bq/l) may be regarded as high, considering the high toxicity of neptunium and its long half-life.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00115976
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 16
    Electronic Resource
    Electronic Resource
    Well modeling and estimation of hydraulic parameters (1997)
    Springer
    Computational geosciences 1 (1997), S. 317-331 
    Details
    ISSN: 1573-1499
    Keywords: well ; hydraulic parameters ; groundwater ; drawdown ; inflow into the well
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Computer Science
    Notes: Abstract A general model for time‐dependent saturated–unsaturated waterflow caused by a single well with a given radius is presented. The storage capacity of the well tube is taken into account. The inflow into the well (with drainage) is modeled using the Signorini boundary condition. The nonconforming mixed finite element method on a multilevel adaptive grid is used for the solution of the radial symmetric, time dependent problem. Finally, van Genuchten parameters of an aquifer are determined from field measurements by inverse computations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011529614975
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 17
    Electronic Resource
    Electronic Resource
    Brine transport in porous media: On the use of Von Mises and similarity transformations (1998)
    Springer
    Computational geosciences 2 (1998), S. 125-149 
    Details
    ISSN: 1573-1499
    Keywords: brine transport ; Von Mises transformation ; similarity transformation ; groundwater ; 35K65 ; 58G11 ; 76S05
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Computer Science
    Notes: Abstract In this paper we use a Von Mises transformation to study brine transport in porous media. The model involves mass balance equations for fluid and salt, Darcy's law and an equation of state, relating the salt mass fraction to the fluid density. Application of the Von Mises transformation recasts the model equations into a single nonlinear diffusion equation. A further reduction is possible if the problem admits similarity. This yields a formulation in terms of a boundary value problem for an ordinary differential equation which can be treated by semi‐analytical means. Three specific similarity problems are considered in detail: (i) one‐dimensional, stable displacement of fresh water and brine in a porous column, (ii) flow of fresh water along the surface of a salt rock, (iii) mixing of parallel layers of brine and fresh water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011598102680
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 18
    Electronic Resource
    Electronic Resource
    Effects of search parameters on kriged reserve estimates (1990)
    Springer
    Geotechnical and geological engineering 8 (1990), S. 305-318 
    Details
    ISSN: 1573-1529
    Keywords: Geostatistics ; kriging ; ore reserve estimation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Summary Reliable ore reserve estimates for deposits with highly skewed grade distributions are difficult tasks to perform. Although some recent geostatistical techniques are available to handle problems with these estimations, ordinary kriging or conventional interpolation methods are still widely used to estimate the ore reserves for such deposits. The estimation results can be very sensitive to the search parameters used during the interpolation of grades with these methods. This paper compares the ore reserve estimates from ordinary kriging using several cases in which certain search parameters are varied. The comparisons are extended to different mineralizations to show the changing effects of these parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00920643
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 19
    Electronic Resource
    Electronic Resource
    Kriging with imprecise (fuzzy) variograms. I: Theory (1990)
    Springer
    Mathematical geology 22 (1990), S. 63-79 
    Details
    ISSN: 1573-8868
    Keywords: kriging ; variogram ; fuzzy set theory ; prior information ; methodology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Imprecise variogram parameters are modeled with fuzzy set theory. The fit of a variogram model to experimental variograms is often subjective. The “accuracy” of the fit is modeled with imprecise variogram parameters. Measurement data often are insufficient to create “good” experimental variograms. In this case, prior knowledge and experience can contribute to determination of the variogram model parameters. A methodology for kriging with imprecise variogram parameters is developed. Both kriged values and estimation variances are calculated as fuzzy numbers and characterized by their membership functions. Besides estimation variance, the membership functions are used to create another uncertainty measure. This measure depends on both homogeneity and configuration of the data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00890297
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 20
    Electronic Resource
    Electronic Resource
    Kriging with imprecise (fuzzy) variograms. II: Application (1990)
    Springer
    Mathematical geology 22 (1990), S. 81-94 
    Details
    ISSN: 1573-8868
    Keywords: application ; permeability prediction ; soil liner ; kriging ; variogram ; fuzzy set theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The geostatistical analysis of soil liner permeability is based on 20 measurements and imprecise prior information on nugget effect, sill, and range of the unknown variogram. Using this information, membership functions for variogram parameters are assessed and the fuzzy variogram is constructed. Both kriging estimates and estimation variances are calculated as fuzzy numbers from the fuzzy variogram and data points. Contour maps are presented, indicating values of the kriged permeability and the estimation variance corresponding to selected membership values called levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00890298
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 21
    Electronic Resource
    Electronic Resource
    A variance of geostatisticians (1990)
    Springer
    Mathematical geology 22 (1990), S. 417-455 
    Details
    ISSN: 1573-8868
    Keywords: Geostatistics ; kriging ; interpolation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Different individuals will take different approaches to the analysis and interpretation of data. This study attempted to quantify the effect of such individual differences on the quality of geostatistical spatial estimates. Identical spatial data sets were sent to 12 investigators, who independently analyzed the data and produced spatial interpolations. The results varied considerably. Differences in the interpolations could be attributed to differences in choice of methodology, differences in data interpretation, and, in a few cases, errors in procedure. The potential differences in economic and societal costs between decisions based on “good” vs. “bad” interpolations warrant a systematic approach to the identification and testing of interpolation methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00890328
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 22
    Electronic Resource
    Electronic Resource
    Problems in space-time kriging of geohydrological data (1990)
    Springer
    Mathematical geology 22 (1990), S. 611-623 
    Details
    ISSN: 1573-8868
    Keywords: geostatistics ; geohydrology ; kriging ; spatiotemporal variables
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Spatiotemporal variables constitute a large class of geohydrological phenomena. Estimation of these variables requires the extension of geostatistical tools into the space-time domain. Before applying these techniques to space-time data, a number of important problems must be addressed. These problems can be grouped into four general categories: (1) fundamental differences with respect to spatial problems, (2) data characteristics, (3) structural analysis including valid models, and (4) space-time kriging. Adequate consideration of these problems leads to more appropriate estimation techniques for spatiotemporal data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00890508
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 23
    Electronic Resource
    Electronic Resource
    Geostatistical cross-validation: A cautionary note (1990)
    Springer
    Mathematical geology 22 (1990), S. 637-639 
    Details
    ISSN: 1573-8868
    Keywords: spatial covariance ; kriging ; geostatistical cross-validation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00890512
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 24
    Electronic Resource
    Electronic Resource
    Application of spatial filter theory to kriging (1990)
    Springer
    Mathematical geology 22 (1990), S. 1063-1079 
    Details
    ISSN: 1573-8868
    Keywords: point-spread function ; spatial filtering ; kriging ; variogram ; digital image ; intrinsic random functions ; conditional simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Data-processing requirements for remotely sensed, digital images include spatial filtering to suppress image noise, enhance edges/contacts, and improve image clarity. Spatial filter theory demonstrates that the addition of a high-pass filtered image to a low-pass filtered image yields the original digital image. Application of this principle in kriging can be accomplished by using the same covariance matrix to solve for two weighting vectors to yield a result analogous to low- and high-pass filtering. The addition of kriged estimates calculated using both weighting vectors is analogous to summing high-, and low-pass filtered digital images. This modified method of kriging yields estimates associated with less smoothing compared to ordinary kriging. Statistical moments of original sample data are better preserved through estimation by this method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00890124
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 25
    Electronic Resource
    Electronic Resource
    Trend-surface analysis (1971)
    Springer
    Mathematical geology 3 (1971), S. 215-226 
    Details
    ISSN: 1573-8868
    Keywords: autocorrelation ; kriging ; regionalized variables ; trend analysis ; geostatistics ; general geology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract This paper is largely an exposition of the work of the French geostatistian G. Matheron and his school in English and at a simpler mathematical level. The probability theory on which it is based is essentially all contained in the references cited, most of which will be unfamiliar to mathematical geologists. The important method of ‘universal kriging” is explained intuitively. The genuine statistical problems, which have yet to be overcome, are pointed out.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02045792
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 26
    Electronic Resource
    Electronic Resource
    Elicited Data and Incorporation of Expert Opinion for Statistical Inference in Spatial Studies (2000)
    Springer
    Mathematical geology 32 (2000), S. 465-487 
    Details
    ISSN: 1573-8868
    Keywords: Bayesian inference ; elicited prior ; hierarchical models ; honesty parameter ; kriging ; optimal sequential sample design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Spatial data are often sparse by nature. However, in many instances, information may exist in the form of “soft” data, such as expert opinion. Scientists in the field often have a good understanding of the phenomenon under study and may be able to provide valuable information on its likely behavior. It is thus useful to have a sensible mechanism that incorporates expert opinion in inference. The Bayesian paradigm suffers from an inherent subjectivity that is unacceptable to many scientists. Aside from this philosophical problem, elicitation of prior distributions is a difficult task. Moreover, an intentionally misleading expert can have substantial influence on Bayesian inference. In our experience, eliciting data is much more natural to the experts than eliciting prior distributions on the parameters of a probability model that is a purely statistical construct. In this paper we elicit data, i.e., guess values for the realization of the process, from the experts. Utilizing a hierarchical modeling framework, we combine elicited data and actual observed data for inferential purposes. A distinguishing feature of this approach is that even an intentionally misleading expert proves to be useful. Theoretical results and simulations illustrate that incorporating expert opinion via elicited data substantially improves the estimation, prediction, and design aspects of statistical inference for spatial data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007525900030
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 27
    Electronic Resource
    Electronic Resource
    Statistical and geostatistical methods applied to the exploration work of the Nanisivik Zn-Pb mine, Baffin Island, Canada (1980)
    Springer
    Mathematical geology 12 (1980), S. 321-337 
    Details
    ISSN: 1573-8868
    Keywords: geostatistics ; kriging ; variogram analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The Nanisivik Pb-Zn deposit at Strathcona Sound, northern Baffin Island, Canada, is an orebody that is an S-shaped lens 3000 m long, 75 m wide, and 2–20 m thick. It is an epigenetic karst channel filling. Total reserves are 6.9 million short tons of 14.12% Zn, 1.4% Pb, and 1.77 oz of Ag per ton. The mine was brought into production in 1976 at a rate of 2000 short tons per day. In the preproduction phase variogram studies based only on surface holes indicated a random distribution. For the evaluation of grades and for the determination of the confidence limits, classic statistical procedures were applied. Since the drilling density was different in different ore zones, a model was developed to test the effect of different drill hole spacings on the uncertainties in the present value in a discounted cash flow model. After the initial development and mining stage, structures could be recognized in semivariograms. Studies for a best drilling grid showed that the pattern of 25 ×20 m used in the mine could be extended to 35 ×35 m, taking into account that eight stopes are mined simultaneously. For ore reserve calculations weighing factors were calculated by kriging for six universally applicable geometric situations. Only the drill holes within a block and immediately surrounding it were taken into account. A test in a well-known zone yielded satisfactory results. A test to predict highs and lows of the grade accurately enough to optimally place the pillars failed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01029419
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 28
    Electronic Resource
    Electronic Resource
    Lognormal kriging—the general case (1982)
    Springer
    Mathematical geology 14 (1982), S. 475-499 
    Details
    ISSN: 1573-8868
    Keywords: kriging ; lognormal estimation ; conservation of lognormality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract A theoretical study of the general case of the estimation of regionalized variables with a lognormal distribution is presented. The results of this study are compared to those obtained assuming conservation of lognormality. The numerical significance of the different solutions is illustrated by several simple examples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01077535
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 29
    Electronic Resource
    Electronic Resource
    Variogram models for regional groundwater geochemical data (1982)
    Springer
    Mathematical geology 14 (1982), S. 629-644 
    Details
    ISSN: 1573-8868
    Keywords: variogram ; kriging ; interpolation ; contouring ; inverse distance weighting ; geochemical gradient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Four variogram models for regional groundwater geochemical data are presented. These models were developed from an empirical study of the sample variograms for more than 10 elements in groundwaters from two geologic regions in the Plainview quandrangle, Texas. A procedure is given for the estimation of the variogram in the isotropic and anisotropic case. The variograms were found useful for quantifying the differences in spatial variability for elements within a geologic unit and for elements in different geologic units. Additionally, the variogram analysis enables assessment of the assumption of statistical independence of regional samples which is commonly used in many statistical procedures. The estimated variograms are used in computation of kriged estimates for the Plainview quadrangle data. The results indicate that an inverse distance weighting model was superior for prediction than simple kriging with the particular variograms used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01033884
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 30
    Electronic Resource
    Electronic Resource
    The combination of sampling and kriging in the regional estimation of coal resources (1982)
    Springer
    Mathematical geology 14 (1982), S. 87-106 
    Details
    ISSN: 1573-8868
    Keywords: coal ; geostatistics ; kriging ; regional estimation ; systematic sampling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Two-dimensional systematic sampling of small plots followed by the kriging of those plots may be employed to obtain regional estimates of coal resources and measures of the accuracy of the estimates. The use of sampling makes large savings in computation possible. Two case studies involving the estimation of coal tonnage are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01083946
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 31
    Electronic Resource
    Electronic Resource
    Geostatistics as a tool to define various categories of resources (1983)
    Springer
    Mathematical geology 15 (1983), S. 131-143 
    Details
    ISSN: 1573-8868
    Keywords: Geostatistics ; resource classification ; mineral resources ; kriging ; resource definitions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Definition of “measured” and “indicated” resources tend to be vague. Yet, the calculation of such categories of resources in a mineral deposit calls for specific technical criteria, the selection of which depends upon the method of evaluation. This paper discusses how a geostatistical methodology provides the technical criteria required to classify reasonably assured resources by levels of assurance of their existence. A preliminary discussion concludes that the reasonably assured resources of a mineral deposit should be classified locally as in the traditional approach. However, the size of local volumes should not correspond to the elementary grid unit of drill holes but if possible to the minimum unit of selection that can be supported by the chosen mining method. The “level of confidence” of the reasonably assured resources can be quantitatively represented and determined by the estimation variance, one of the most important tools of geostatistics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01030079
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 32
    Electronic Resource
    Electronic Resource
    Kriging of water levels in the Souss aquifer, Morocco (1983)
    Springer
    Mathematical geology 15 (1983), S. 537-551 
    Details
    ISSN: 1573-8868
    Keywords: kriging ; drift ; least squares ; residuals ; water table
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Universal kriging is applied to water table data from the Souss aquifer in central Morocco. The procedure accounts for the spatial variability of the phenomenon to be mapped. With the use of measured elevations of the water table, an experimental variogram is constructed that characterizes the spatial variability of the measured water levels. Spherical and Gaussian variogram models are alternatively used to fit the experimental variogram. The models are used to develop contour maps of water table elevations and corresponding estimation variances. The estimation variances express the reliability of the kriged water table elevation maps. Universal kriging also provides a contour map of the expected elevation of the water table (drift). The differences between the expected and measured water table elevations are called residuals from the drift. Residuals from the drift are compared with residuals obtained by more traditional least-squares analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01031176
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 33
    Electronic Resource
    Electronic Resource
    Robust kriging—A proposal (1984)
    Springer
    Mathematical geology 16 (1984), S. 3-18 
    Details
    ISSN: 1573-8868
    Keywords: Geostatistics ; kriging ; robust estimation ; time series
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Geological data frequently have a heavy-tailed normal-in-the-middle distribution, which gives rise to grade distributions that appear to be normal except for the occurrence of a few outliers. This same situation also applies to log-transformed data to which lognormal kriging is to be applied. For such data, linear kriging is nonrobust in that (1)kriged estimates tend to infinity as the outliers do, and (2)it is also not minimum mean squared error. The more general nonlinear method of disjunctive kriging is even more nonrobust, computationally more laborious, and in the end need not produce better practical answers. We propose a robust kriging method for such nearly normal data based on linear kriging of an editing of the data. It is little more laborious than conventional linear kriging and, used in conjunction with a robust estimator of the variogram, provides good protection against the effects of data outliers. The method is also applicable to time series analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01036237
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 34
    Electronic Resource
    Electronic Resource
    Autorun analysis of sedimentary porous materials (1984)
    Springer
    Mathematical geology 16 (1984), S. 449-463 
    Details
    ISSN: 1573-8868
    Keywords: autorun function ; groundwater ; porosity ; random field ; simulation ; specific surface
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Fundamentals of autorun analysis have been given to describe porous media geometry, including sedimantary rocks. The mathematical abstraction of porous media has been presented on the basis of random fields. Classical parameters of porous media, such as porosity and specific surface, have been expressed in terms of autorun function. Finally, a stochastic model has been proposed for the underlying generating mechanism of the porous medium. This model is capable of producing synthetic porous medium and, on the average, porosity as well as the specific surface. The first autorun coefficient is asymptotically equal to the porosity of the medium concerned. It also has been observed that the porosity together with the autorun function are sufficient to produce the specific surface value of the medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01886326
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 35
    Electronic Resource
    Electronic Resource
    Smoothing and interpolation by kriging and with splines (1984)
    Springer
    Mathematical geology 16 (1984), S. 601-615 
    Details
    ISSN: 1573-8868
    Keywords: kriging ; splines ; interpolation ; smoothing ; prediction ; Green's function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Let scalar measurements at distinct points x1, ⋯, xn be y1, ⋯, yn.We may look for a smooth function f(x)that goes through or near the points (xi, yi).Kriging assumes f(x)is a random function with known (possibly estimable) covariance function (in the simplest case). Splines assume a definition of the smoothness of a nonrandom function f(x).An elementary explanation is given of the fact that spline approximations are special cases of the solution of a kriging problem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01029320
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 36
    Electronic Resource
    Electronic Resource
    Cross validation of kriging in a unique neighborhood (1983)
    Springer
    Mathematical geology 15 (1983), S. 687-699 
    Details
    ISSN: 1573-8868
    Keywords: cross validation ; kriging ; moving neighborhood ; unique neighborhood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Cross validation is an appropriate tool for testing interpolation methods: it consists of leaving out one data point at a time, and determining how well this point can be estimated from the other data. Cross validation is often used for testing “moving neighborhood” kriging models; in this case, each unknown value is predicted from a small number of surrounding data. In “unique neighborhood” kriging algorithms, each estimation uses all the available data; as a result, cross validation would spend much computer time. For instance, with ndata points it would cost at least the resolution of nsystems of n × nlinear equations (each with a different matrix).Here, we present a much faster method for cross validation in a unique neighborhood. Instead of solving nsystems n × n,it only requires the inversion of one n × nmatrix. We also generalized this method to leaving out several points instead of one.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01033232
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 37
    Electronic Resource
    Electronic Resource
    Cokriging of aquifer transmissivities from field measurements of transmissivity and specific capacity (1984)
    Springer
    Mathematical geology 16 (1984), S. 19-35 
    Details
    ISSN: 1573-8868
    Keywords: groundwater ; geostatistics ; cokriging ; kriging ; transmissivity ; specific capacity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract This paper presents a new application of the cokriging technique for constructing maps of aquifer transmissivity from field measurements of transmissivity and specific capacity. The technique is illustrated using data from Yolo Basin, California. Cokriging is well-suited for estimating undersampled variables. To improve the accuracy of the estimation, cokriging considers the spatial auto-correlation of the variable to be estimated and the spatial cross-correlation between the variable to be estimated and other, better-sampled variables. Consequently, in regions that lack data of the variable to be estimated, accurate estimation can still be made on the basis of auto- and cross-correlation. In addition, estimation variances can be obtained with a little additional computation effort.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01036238
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 38
    Electronic Resource
    Electronic Resource
    A geostatistically based approach to the identification of aquifer transmissivities in Yolo Basin, California (1984)
    Springer
    Mathematical geology 16 (1984), S. 125-137 
    Details
    ISSN: 1573-8868
    Keywords: kriging ; cokriging ; hydrology ; groundwater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract A geostatistically based approach is developed for the identification of aquifer transmissivities in Yolo Basin, California. The approach combines weighted least-squares with universal kriging and cokriging techniques in an overall scheme that (1)considers a prioriknown information on aquifer transmissivity and specific capacities of wells, (2)considers uncertainties in water level and transmissivity data, and (3)estimates the reliability of the generated transmissivity values. Minimization of a global least-squares function that incorporates calibration and plausibility criteria leads to a transmissivity map that shows a good agreement with pumping-test results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01032212
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 39
    Electronic Resource
    Electronic Resource
    Treatment of earthquake ground motion using regionalized variables (1985)
    Springer
    Mathematical geology 17 (1985), S. 221-241 
    Details
    ISSN: 1573-8868
    Keywords: variograms ; covariance ; positive definite conditions ; kriging ; Modified Mercalli Intensity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Earthquake ground motion is a spatial phenomenon associated with local random behavior and global attenuation away from a source. By this description, ground motion is a regionalized variable. Analyses of directional variograms for earthquake ground motion reveal ansiotropic attenuation. For some earthquakes, a spatial structure exists in all directions and an average variogram can be developed. For other earthquakes, either a spatial structure can be identified only for restricted directions, or a spatial structure cannot be found to exist in any direction. A valid application of regionalized variables theory to the spatial analysis of earthquake ground motion must therefore be predicated on an initial, exhaustive analysis of estimated variograms. To estimate these data, an application of ordinary kriging is preferable to other more complex regionalized variables techniques to simplify the spatial analysis of earthquake ground motion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01034751
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 40
    Electronic Resource
    Electronic Resource
    Analysis of nonintrinsic spatial variability by residual kriging with application to regional groundwater levels (1984)
    Springer
    Mathematical geology 16 (1984), S. 499-521 
    Details
    ISSN: 1573-8868
    Keywords: Spatial variability ; nonintrinsic ; nonstationary ; drift ; kriging ; residuals ; groundwater levels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract A method for obtaining pointwise or spatially averaged estimates of a nonintrinsic function is introduced based on residual kriging. The method relies on a stepwise iterative regression process for simultaneously estimating the global drift and residual semivariogram. Estimates of the function are then obtained by solving a modified set of simple kriging equations written for the residuals. The modification consists of replacing the true variogram in the kriging equations by the variogram of the residual estimates as obtained from the iterative regression process. The method is illustrated by considering groundwater levels in an Arizona aquifer. The results are compared with those obtained for the aquifer by the generalized covariance package BLUEPACK-3D.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01886329
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 41
    Electronic Resource
    Electronic Resource
    Global estimation variance: Formulas and calculation (1985)
    Springer
    Mathematical geology 17 (1985), S. 785-796 
    Details
    ISSN: 1573-8868
    Keywords: geostatistics ; kriging ; estimation variance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract This paper discusses the combination of kriging variances, which have been considered heretofor unfeasible since linearity of the problem and considerable simplifications which follow were overlooked. A simplified expression for global estimation variance is presented and an algorithm discussed with respect to precision and computer cost. A case study is presented, and, finally, an optimum calculation method is recommended.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01034061
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 42
    Electronic Resource
    Electronic Resource
    An interpolation method taking into account inequality constraints: II. Practical approach (1986)
    Springer
    Mathematical geology 18 (1986), S. 53-73 
    Details
    ISSN: 1573-8868
    Keywords: kriging ; mapping ; quadratic programming ; isopachs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Common features of models for interpolation, consistent with a finite number of inequality constraints on the range of values of a variablez, are discussed. A method based on constrained quadratic minimization yielding kriging estimates when no constraints exist, is presented. A computationally efficient formulation of quadratic minimization is obtained by using results on duality in quadratic programming. Relevant properties of the optimal interpolator are derived in a simple, self-contained way. The method is applied to mapping of horizon depth and estimation of thickness of an oil-bearing formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00897655
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 43
    Electronic Resource
    Electronic Resource
    Single/multiple input-single output transfer function with noise models for constituents of iron ores of Northern Goa, India (1985)
    Springer
    Mathematical geology 17 (1985), S. 755-767 
    Details
    ISSN: 1573-8868
    Keywords: time (spatial) series ; prewhitening ; feedback ; transfer function ; residual variance ; forecasting ; kriging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Parametric time domain time series models for different chemical constituents such as SiO 2,Fe 2 O 3,TiO 2,MnO, and P 2 O 5 of iron ores belonging to banded hematite quartzites in Bicholim Mine (Goa) have been utilized for forecasting Fe 2 O 3 assay values through single/multiple input—single output (Fe 2 O 3 ) transfer function with noise methodology. Statistically significant correlated chemical constituent inputs (say, SiO 2,TiO 2,MnO, P 2 O 5 ) along lateral (horizontal strike direction) and vertical (perpendicular to bedding planes) sections in this mine are useful in modeling as well as forecasting assay values of blocks of ore to be exploited. Parameters of transfer function—noise models are estimated by utilizing time domain methodology, and the usefulness of these models for optimization of mining operations is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01031615
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 44
    Electronic Resource
    Electronic Resource
    An interpolation method taking into account inequality constraints: I. Methodology (1986)
    Springer
    Mathematical geology 18 (1986), S. 33-51 
    Details
    ISSN: 1573-8868
    Keywords: kriging ; splines ; mapping ; prediction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Several kinds of data can provide information about a variable measured on a one- or two-dimensional space; at some points, the value is known to be equal to a certain number. At other points, the only information may be that the variable is greater or smaller than a given value. The theory of splines provides interpolating functions that can take into account both equality and inequality data. These interpolating functions are presented. The parallel between splines and kriging is reviewed, using the formalism of dual kriging. Coefficients of dual kriging can be obtained directly by minimizing a quadratic form. By adding some inequality constraints to this minimization, an interpolating function may be calculated which takes into account inequality data and is more general than a spline. The method is illustrated by some simple one-dimensional examples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00897654
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 45
    Electronic Resource
    Electronic Resource
    A sensitivity analysis for universal kriging (1986)
    Springer
    Mathematical geology 18 (1986), S. 653-676 
    Details
    ISSN: 1573-8868
    Keywords: approximate analysis ; covariance model ; kriging ; perturbation surface ; sensitivity analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Universal kriging is an interpolation method for producing contour maps from irregularly spaced sample points, taking into account the trend (or polynomial drift), which is of known form. It assumes a known covariance model to express correlation of points a short distance apart. A sensitivity analysis examines how the fitted surface will change for given perturbations in the covariance model. We develop a simple approximate analysis in preference to exact analysis and show that it is adequate for small perturbations. For large data sets, a dramatic reduction in computer time is possible using approximate analysis. Possible extensions of this work are noted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00897095
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 46
    Electronic Resource
    Electronic Resource
    Bayesian kriging—Merging observations and qualified guesses in kriging (1987)
    Springer
    Mathematical geology 19 (1987), S. 25-39 
    Details
    ISSN: 1573-8868
    Keywords: geostatistics ; kriging ; Bayesian statistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Frequently a user wants to merge general knowledge of the regionalized variable under study with available observations. Introduction of fake observations is the usual way of doing this. Bayesian kriging allows the user to specify a qualified guess, associated with uncertainty, for the expected surface. The method will provide predictions which are based on both observations and this qualified guess.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01275432
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 47
    Electronic Resource
    Electronic Resource
    Production of conditional simulations via the LU triangular decomposition of the covariance matrix (1987)
    Springer
    Mathematical geology 19 (1987), S. 91-98 
    Details
    ISSN: 1573-8868
    Keywords: geostatistics ; kriging ; conditional simulation ; fast Fourier transform
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract This paper reviews the turning band method and fast Fourier transform method of producing a nonconditional simulation of a multinormal random function with a given covariance structure. A review of the two common methods of conditioning the simulation to honor the data shows that they are formally equivalent. Another method for directly pondering a conditional simulation based on the LU triangular decomposition of the covariance matrix is presented. Computational and implementation difficulties are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00898189
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 48
    Electronic Resource
    Electronic Resource
    Interval-valued random functions and the kriging of intervals (1988)
    Springer
    Mathematical geology 20 (1988), S. 145-165 
    Details
    ISSN: 1573-8868
    Keywords: interval-valued data ; random function ; kriging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Estimation procedures using data that include some “values” known to lie within certain intervals are usually regarded as problems of constrained optimization. A different approach is used here. Intervals are treated as elements of a positive cone, obeying the arithmetic of interval analysis, and positive interval-valued random functions are discussed. A kriging formalism for interval-valued data is developed. It provides estimates that are themselves intervals. In this context, the condition that kriging weights be positive is seen to arise in a natural way. A numerical example is given, and the extension to universal kriging is sketched.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00890251
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 49
    Electronic Resource
    Electronic Resource
    Spatial prediction and ordinary kriging (1988)
    Springer
    Mathematical geology 20 (1988), S. 405-421 
    Details
    ISSN: 1573-8868
    Keywords: kriging ; nugget effect ; range ; sill ; variogram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Suppose data {Z(s i ):i=1, ..., n} are observed at spatial locations {s i :i=1, ..., n}. From these data, an unknownZ(s 0) is to be predicted at a known locations 0c, or, ifZ(s0) has a component of measurement error, then a smooth versionS(s 0) should be predicted. This article considers the assumptions needed to carry out the spatial prediction using ordinary kriging, and looks at how nugget effect, range, and sill of the variogram affect the predictor. It is concluded that certain commonly held interpretations of these variogram parameters should be modified.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00892986
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 50
    Electronic Resource
    Electronic Resource
    New distance measures: The route toward truly non-Gaussian geostatistics (1988)
    Springer
    Mathematical geology 20 (1988), S. 459-475 
    Details
    ISSN: 1573-8868
    Keywords: Projection theorem ; kriging ; scalar product ; heteroscedasticity ; outlier resistance ; variogram ; distance measure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The projection or minimum error norm algorithm does not require that the distance measure be a variogram. In non-Gaussian cases, the traditional variogram distance measure leading to minimization of an error variance offers no definite advantage. Other distance measures, more outlierresistant than the variogram, are proposed which fulfill the condition of the projection theorem. The resulting minimum error norms provide the same data configurations ranking as traditionally obtained from kriging variances. A case study based on actual digital terrain data is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00892989
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 51
    Electronic Resource
    Electronic Resource
    Bootstrapped models for intrinsic random functions (1988)
    Springer
    Mathematical geology 20 (1988), S. 699-715 
    Details
    ISSN: 1573-8868
    Keywords: Regionalized variables ; kriging ; interpolation ; sample reuse ; nonparametric error estimates ; confidence intervals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Use of intrinsic random function stochastic models as a basis for estimation in geostatistical work requires the identification of the generalized covariance function of the underlying process. The fact that this function has to be estimated from data introduces an additional source of error into predictions based on the model. This paper develops the sample reuse procedure called the “bootstrap” in the context of intrinsic random functions to obtain realistic estimates of these errors. Simulation results support the conclusion that bootstrap distributions of functionals of the process, as well as their “kriging variance,” provide a reasonable picture of variability introduced by imperfect estimation of the generalized covariance function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00890586
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 52
    Electronic Resource
    Electronic Resource
    Assessment of Nitrate—Nitrogen Distribution in Kansas Groundwater, 1990–1998 (2000)
    Springer
    Natural resources research 9 (2000), S. 125-134 
    Details
    ISSN: 1573-8981
    Keywords: Geographic area ; depth of well ; age of well ; groundwater ; nitrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Nitrate-nitrogen (nitrate-N) in groundwater is a potential problem in many parts of Kansas.From 1990 to 1998, 747 water samples were collected from domestic, irrigation, monitoring,and public water supply wells primarily from the western two-thirds of the state, and analyzedfor nitrate-N by the Kansas Geological Survey. Nitrate-N concentrations of the 747 samplesanalyzed range from 29% with less than or equal to 3 mg/L, 51% between 3 and 10 mg/L,and 20% greater than or equal to 10 mg/L. Factors that show a statistically significantrelationship with the occurrence of nitrate-N in Kansas groundwater in this assessment includegeographic area of the state, depth of well, and age of well. Nitrate-N levels of wells screenedin the High Plains aquifer in south-central Kansas showed a statistically higher concentrationthan samples collected from the High Plains aquifer in the western portion of the state.Comparison of nitrate-N with depth of well indicated that shallower wells throughout the stategenerally have higher nitrate-N values than deeper wells. Irrigation wells older than 1975showed statistically higher nitrate-N concentration than wells installed during and since 1975,possibly related to changes in well-construction practices and regulations that occurred in 1975.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010143426576
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 53
    Electronic Resource
    Electronic Resource
    Natural Geological Weighing Lysimeters: Calibration Tools for Satellite and Ground Surface Gravity Monitoring of Subsurface Water-Mass Change (2000)
    Springer
    Natural resources research 9 (2000), S. 147-156 
    Details
    ISSN: 1573-8981
    Keywords: Gravity ; hydrology ; lysimeter ; GRACE ; aquifer ; groundwater ; storage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Increased accuracy in measuring temporal variations in the Earth's gravity field allow inprinciple the use of gravity observations to deduce subsurface water-mass changes. This canbe with respect to a small area, or as a larger spatial average of water mass change usinggravity observations from low-altitude satellites, such as the forthcoming GRACE mission.At both scales, there is a need to validate gravity-based estimates against field recordings ofactual subsurface water-mass variations. In practice, this could prove difficult because thespatial integral of all water-storage change components can be subject to considerable fieldmeasurement error. An alternative approach to the validation process is proposed by whichsuitable geological formations are utilized as giant weighing devices to directly measure area-integratedwater-mass changes. The existence of such “natural geological weighing lysimeters”is demonstrated using observations from a replicated experimental site in New Zealand. Sitesof this type could be used to verify water-storage change estimates derived from sensitiveground surface gravity instrumentation. In addition, geological lysimeters could be used tomake local checks on the accuracy of any estimated regional water-mass time series, whichis proposed for satellite calibration. The land area “weighed” by a geological lysimeter increaseswith formation depth and it is speculated that recordings made at oil well depth may allowdirect monitoring of subsurface water mass changes at the regional scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010147527484
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 54
    Electronic Resource
    Electronic Resource
    Water-table variation in a sloping aquifer due to random recharge (1996)
    Springer
    Water resources management 10 (1996), S. 241-250 
    Details
    ISSN: 1573-1650
    Keywords: groundwater ; aquifer ; water table ; drainage ; random recharge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract Variation in the level of the water table is closely linked with recharge. Therefore, any uncertainty associated with the recharge rate is bound to affect the nature of the water-table fluctuation. In this note, a ditch-drainage problem of a sloping aquifer is considered to investigate the effect of uncertainty in the recharge rate on water-table fluctuation. The rate of recharge is taken as an exponentially decaying function with its decay constant as a Gaussian random variable. Expressions for the first two moments of the water-table height, i.e. mean and standard deviation, are presented. By using these expressions, the effect of uncertainty in the recharge rate on the water-table fluctuation has been analyzed with the help of a numerical example.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00424205
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 55
    Electronic Resource
    Electronic Resource
    Application of particle methods to reliable identification of groundwater pollution sources (1992)
    Springer
    Water resources management 6 (1992), S. 15-23 
    Details
    ISSN: 1573-1650
    Keywords: Particle methods ; random walk ; reversed time simulation ; conditional simulation ; kriging ; Monte Carlo simulations ; correlation length ; turning bands method ; inter-sampling distance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract An alternative strategy for identifying sources of contamination in groundwater systems is presented. Under the assumption that the remediation cost is affected by the level of contamination, the proposed scheme provides probabilistic estimates of source locations and spill-time histories. Moreover, the method successfully assesses the relative importance of each potential source.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00872184
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 56
    Electronic Resource
    Electronic Resource
    Appraisal and optimization of agricultural water use in large irrigation schemes: II. Applications (1992)
    Springer
    Water resources management 6 (1992), S. 201-221 
    Details
    ISSN: 1573-1650
    Keywords: Argentina ; groundwater ; irrigation ; simulation model ; surface water ; water use
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract In this paper, the theoretical approach presented in Part I is demonstrated by means of case studies on the irrigation schemes of Rio Mendoza and Rio Tunuyán in the Province of Mendoza, Argentina. The object of the case studies was the determination of optimal allocation of surface water to reduce the use of groundwater. Current and optimal conjunctive allocation of ground and surface water is studied by means of the developed simulation and optimization models. The second case study was designed on the basis of the experience gathered during the first one: each step of the case studies is compared. The comparison between the two case studies illustrates how to apply the proposed approach when the amount and quality of available data are different. For the more detailed Rio Tunuyán study, we determined the following physical characteristics of all terminal nodes: on-farm rotational intervals, mean water application depth, actual soil water storage capacity, crop water requirements, depth of groundwater table, aquifer transmissivity, and efficiency of groundwater use. The performance of the entire system is sensitive to changes in the water application depth, as it was shown by a simulation study. The application of our optimization approach to the conjunctive use of ground- and surface water showed that the total water requirements over a year can be met by a reassignment of water that reduces the total costs of a great amount.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00872356
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 57
    Electronic Resource
    Electronic Resource
    Mathematical models for saltwater intrusion in coastal aquifers (1993)
    Springer
    Water resources management 7 (1993), S. 3-37 
    Details
    ISSN: 1573-1650
    Keywords: Coastal aquifers ; saltwater intrusion ; groundwater ; mathematical models ; analytical and numerical models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract Flow of freshwater and saltwater intrusion in coastal aquifers has drawn the attention of many investigators. Several laboratory, as well as mathematical models have been developed to study the pattern of flow of groundwater in coastal aquifers. Mathematical models have wider range of application and are the concern of this paper. Due to the complex nature of the problem, each of these mathematical models are based on certain simplifying assumptions and approximations. This paper presents a critical review of various methods of solution which have been proposed. The validity of the results abtained and the limitations of these models are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00872240
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 58
    Electronic Resource
    Electronic Resource
    Modeling Variable Density Flow and Solute Transport in Porous Medium: 2. Re‐Evaluation of the Salt Dome Flow Problem (1999)
    Springer
    Transport in porous media 35 (1999), S. 375-394 
    Details
    ISSN: 1573-1634
    Keywords: groundwater ; density driven flow ; numerical simulation ; salt dome.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Case 5, Level 1 of the international HYDROCOIN groundwater flow modeling project is an example of idealized flow over a salt dome. The groundwater flow is strongly coupled to solute transport since density variations in this example are large (20%). Several independent teams simulated this problem using different models. Results obtained by different codes can be contradictory. We develop a new numerical model based on the mixed hybrid finite elements approximation for flow, which provides a good approximation of the velocity, and the discontinuous finite elements approximation to solve the advection equation, which gives a good approximation of concentration even when the dispersion tensor is very small. We use the new numerical model to simulate the salt dome flow problem. In this paper we study the effect of molecular diffusion and we compare linear and non‐linear dispersion equations. We show the importance of the discretization of the boundary condition on the extent of recirculation and the final salt distribution. We study also the salt dome flow problem with a more realistic dispersion (very small dispersion tensor). Our results are different to prior works with regard to the magnitude of recirculation and the final concentration distribution. In all cases, we obtain recirculation in the lower part of the domain, even for only dispersive fluxes at the boundary. When the dispersion tensor becomes very small, the magnitude of recirculation is small. Swept forward displacement could be reproduced by using finite difference method to compute the dispersive fluxes instead of mixed hybrid finite elements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006504326005
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 59
    Electronic Resource
    Electronic Resource
    An Integrated Model for the Danubian Lowland – Methodology and Applications (1998)
    Springer
    Water resources management 12 (1998), S. 433-465 
    Details
    ISSN: 1573-1650
    Keywords: Danube ; environmental impacts ; floodplain ; Gabcikovo ; groundwater ; hydropower ; integrated modelling ; river branch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract A unique integrated modelling system has been developed and applied for environmental assessment studies in connection with the Gabcikovo hydropower scheme along the Danube. The modelling system integrates model codes for describing the reservoir (2D flow, eutrophication, sediment transport), the river and river branches (1D flow including effects of hydraulic control structures, water quality, sediment transport), the ground water (3D flow, solute transport, geochemistry), agricultural aspects (crop yield, irrigation, nitrogen leaching) and flood plain conditions (dynamics of inundation pattern, ground water and soil moisture conditions, and water quality). The uniqueness of the established modelling system is the integration between the individual model codes, each of which provides complex descriptions of the various processes. The validation tests have generally been carried out for the individual models, whereas only a few tests on the integrated model were possible. Based on discussion and examples, it is concluded that the results from the integrated model can be assumed less uncertain than outputs from the individual model components. In an example, the impacts of the Gabcikovo scheme on the ecologically unique wetlands created by the river branch system downstream of the new reservoir have been simulated. In this case, the impacts of alternative water management scenarios on ecologically important factors such as flood frequency and duration, depth of flooding, depth to ground water table, capillary rise, flow velocities, sedimentation and water quality in the river system have been explicitly calculated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008088901770
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 60
    Electronic Resource
    Electronic Resource
    Microbiological groundwater quality and health indicators in Mexico City (2000)
    Springer
    Urban ecosystems 4 (2000), S. 91-103 
    Details
    ISSN: 1573-1642
    Keywords: bacterial indicators ; health indicators ; groundwater ; water quality ; Mexico City
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Groundwater quality was evaluated in the southern and western zones of Mexico City, using bacterial indicators and pathogens. Water quality from 40 wells was related to rates of diarrheal disease with 995 individuals interviewed. The focus of this first study on environmental health indicators (EHI) was based on population data (e.g., drinking water supplies and basic sanitation) and displayed using a Geographic Information System (GIS). Sixty percent of the wells monitored comply with the Mexican drinking water standards; however, based on other microbial evidence, 95% of the wells did not provide good quality water for human consumption. No significant differences were detected among hydrogeological zones. When analyzing by microbial indicators, the southern area was shown to be statistically different (p 〈 0.01) from the western area of the city. The highest rates of diarrheal diseases were detected in the south; the lowest rates were observed in the west. Although wells in the western side of the city appeared to be more contaminated (54%) than in the south (40%), no significant association with health indicators was detected. These preliminary findings suggest ways to improve the potential of EHI, by framing epidemiological data and the use of GIS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011334326405
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 61
    Electronic Resource
    Electronic Resource
    Two approaches to modeling unstable flow and mixing of variable density fluids in porous media (1996)
    Springer
    Transport in porous media 23 (1996), S. 219-236 
    Details
    ISSN: 1573-1634
    Keywords: groundwater ; gravitational instability ; fingering ; variable density fluids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Density variation of aqueous phase fluids flowing in a porous medium, resulting from spatial and temporal variation of solute concentration, often gives rise to unstable flow, and therefore has a significant effect on solute transport. Studies on simulating unstable flow and mixing of variable density fluids in seemingly homogeneous porous media are rare. In this study, a three-dimensional (3-D) and a one-dimensional (1-D) model were developed to simulate unstable flow and mixing in a vertical, nominally 1-D system. In the 3-D model, the fluid flow and solute transport equations were solved numerically with a very fine spatial discretization. The 1-D numerical model was derived from a theoretical model to simulate the flow and mixing of fluids with variable density and viscosity at the field scale. To evaluate the models, simulated results were compared with experimental data from displacement experiments in a vertical sand column. The results show that the 1-D model provides fairly good prediction of breakthrough curves and that the 3-D model is able to qualitatively simulate breakthrough curves for highly unstable flow and mixing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00178127
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 62
    Electronic Resource
    Electronic Resource
    Application of remote sensing technology for groundwater potential evaluation (1995)
    Springer
    Water resources management 9 (1995), S. 161-173 
    Details
    ISSN: 1573-1650
    Keywords: Toposheet ; lineaments ; georesistivity ; geomorphology ; drainage ; groundwater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract With the help of the information drawn from a survey of India toposheet and by visual interpretation of satellite imagery of bands 2, 3 and 4, different thematic maps such as geomorphology and lineaments, drainage and land use, and land cover were prepared. These thematic maps have been superimposed and finally a groundwater potential zone map delineated on a survey of India toposheet. The whole block has been demarcated into 5 zones. Zones 1 and 2 are considered ideal groundwater potential areas, zone 3 is moderately ideal, and zones 4 and 5 are unfavourable for groundwater exploration. The validity of demarcation of the study area into different zones, as decided by remote sensing technology, has been justified by analysing the georesistivity sounding data of a number of places in this area. The net potential of the study area is estimated by GEC norm. It is observed that only 11.8% of annual utilisable groundwater is now used and there is vast scope of further exploitation of this resource.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00872127
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 63
    Electronic Resource
    Electronic Resource
    Non-Newtonian Flow in a Variable Aperture Fracture (1998)
    Springer
    Transport in porous media 30 (1998), S. 75-86 
    Details
    ISSN: 1573-1634
    Keywords: fracture ; aperture ; heterogeneity ; non-Newtonian ; power-law fluid ; groundwater ; transmissivity ; nonlinear seepage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The transmissivity of a variable aperture fracture for flow of a non-Newtonian, purely viscous power-law fluid with behavior index n is studied. The natural logarithm of the fracture aperture is considered to be a two-dimensional, spatially homogeneous and correlated Gaussian random field. We derive an equivalent fracture aperture for three flow geometries: (1) flow perpendicular to aperture variation; (2) flow parallel to aperture variation; (3) flow in an isotropic aperture field. Under ergodicity, results are obtained for cases 1 and 2 by discretizing the fracture into elements of equal aperture and assuming that the resistances due to each aperture element are, respectively, in parallel and in series; for case 3, the equivalent aperture is derived as the geometric mean of cases 1 and 2. When n=1 all our expressions for the equivalent aperture reduce to those derived in the past for Newtonian flow and lognormal aperture distribution. As log-aperture variance increases, the equivalent aperture is found to increase for case 1, to decrease for case 2, and to be a function of flow behavior index n for case 3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006512822518
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 64
    Electronic Resource
    Electronic Resource
    On the Influence of Pore-Scale Dispersion in Nonergodic Transport in Heterogeneous Formations (1998)
    Springer
    Transport in porous media 30 (1998), S. 57-73 
    Details
    ISSN: 1573-1634
    Keywords: groundwater ; nonergodic transport ; dispersion ; heterogeneous formations ; hydrogeology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Flow of an inert solute in an heterogeneous aquifer is usually considered as dominated by large-scale advection. As a consequence, the pore-scale dispersion, i.e. the pore scale mechanism acting at scales lower than that characteristic of the heterogeneous field, is usually neglected in the computation of global quantities like the solute plume spatial moments. Here the effect of pore-scale dispersion is taken into account in order to find its influence on the longitudinal asymptotic dispersivity D11we examine both the two-dimensional and the three-dimensional flow cases. In the calculations, we consider the finite size of the solute initial plume, i.e. we analyze both the ergodic and the nonergodic cases. With Pe the Péclat number, defined as Pe=Uλ/D, where U, λ, D are the mean fluid velocity, the heterogeneity characteristic length and the pore-scale dispersion coefficient respectively, we show that the infinite Péclat approximation is in most cases quite adequate, at least in the range of Péclat number usually encountered in practice (Pe 〉 102). A noteworthy exception is when the formation log-conductivity field is highly anisotropic. In this case, pore-scale may have a significant impact on D11, especially when the solute plume initial dimensions are not much larger than the heterogeneities' lengthscale. In all cases, D11 appears to be more sensitive to the pore-scale dispersive mechanisms under nonergodic conditions, i.e. for plume initial size less than about 10 log-conductivity integral scales.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006548529015
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 65
    Electronic Resource
    Electronic Resource
    Modeling Variable Density Flow and Solute Transport in Porous Medium: 1. Numerical Model and Verification (1999)
    Springer
    Transport in porous media 35 (1999), S. 345-373 
    Details
    ISSN: 1573-1634
    Keywords: groundwater ; density driven flow ; numerical simulation ; mixed finite elements ; discontinuous finite elements ; Elder problem.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A new numerical model for the resolution of density coupled flow and transport in porous media is presented. The model is based on the mixed hybrid finite elements (MHFE) and discontinuous finite elements (DFE) methods. MHFE is used to solve the flow equation and the dispersive part of the transport equation. This method is more accurate in the calculation of velocities and ensures continuity of fluxes from one element to the adjacent one. DFE is used to solve the convective part of the transport equation. Combined with a slope limiting procedure, it avoids numerical instabilities and creates a very limited numerical dispersion, even for high grid Peclet number. Flow and transport equations are coupled by a standard iterative scheme. Residual based criterion is used to stop the iterations. Simulations of an unstable equilibrium show the effects of the criteria used to stop the iterations and the stopping criterion in the solver. The effects are more important for finer grids than for coarser grids. The numerical model is verified by the simulation of standard benchmarks: the Henry and the Elder test cases. A good agreement is found between the revised semi‐analytical Henry solution and the numerical solution. The Elder test case was also studied. The simulations were similar to those presented in previous works but with significantly less unknowns (i.e. coarser grids). These results show the efficiency of the used numerical schemes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006564309167
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 66
    Electronic Resource
    Electronic Resource
    Field Investigations for Sustainable Groundwater Utilization in the Konan Basin (1999)
    Springer
    Water resources management 13 (1999), S. 443-470 
    Details
    ISSN: 1573-1650
    Keywords: freshwater crisis ; groundwater ; hydrogeology ; Japan ; konan basin ; pumping-tests ; safe pumpage ; sustainable water supply
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract The Konan groundwater basin of Kochi Prefecture, Japan, is experiencing freshwater shortages for the past few years, particularly during the winter season. The present study aimed at analyzing the problem and exploring increased groundwater withdrawals to meet burgeoning freshwater demands in various sectors. The trend analysis of waterconsumption indicates that the groundwater demandwould increase by 43 and 52% by the years 2010 and2025, respectively, compared to 32 100 m3 d-1 at present.The streamflow of the Monobe River reduces to a minimumin winter and it shows a decreasing trend in recentyears. The geologic investigation results indicatethat unconfined (phreatic) aquifers comprisingalluvial sand and gravel and/or diluvial silty sandand gravel are dominant, and that the northwestern andwestern portions of the basin have greater potentialfor groundwater. Groundwater flows essentially fromnorth to south into the ocean. Groundwater levelfluctuations over the basin vary appreciably in spaceand time, indicating a wide variation of naturalrecharge. Field observations confirm the hypothesisthat stream-aquifer interaction also significantlycontributes to groundwater recharge, besides therainfall infiltration. Further, the pumping testsresults demonstrate that though the aquifers arelow-yielding, enhanced groundwater withdrawals couldbe possible. The aquifer hydraulic conductivity ischaracterized as high and ranges from 65 to 804 m d-1(mean = 229 m d-1), thereby suggesting great aquiferheterogeneity. Finally, it is concluded that thelong-term sustainability of the scarce groundwaterresource of the Konan basin is doubtful, and that acomprehensive analysis of the groundwater system isessential prior to formulating plans for the futuregroundwater development and management.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008184010262
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 67
    Electronic Resource
    Electronic Resource
    The artificial recharge of groundwater: A solution by successive variations of steady states (1989)
    Springer
    Water resources management 3 (1989), S. 231-239 
    Details
    ISSN: 1573-1650
    Keywords: Artificial recharge ; well ; successive variation of steady state ; groundwater ; action radius ; finite elements ; dimensionless graphs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract The artificial recharge of groundwater aims at the modification of water quality, an increase of groundwater resources, and the optimization of the exploitation and recovery of contaminated aquifers. The purpose of this work is to develop a new mathematical model for the problem of an artificial recharge well, using the method of successive variations of steady states. Applying this method, one arrives at an expression of time as a double integral. This integral contains the time-dependent radius of the recharge boundary and the piezometric head of the well, calculated with the finite-element method. The new model is simple and useful, and can be applied to many practical problems, using the designed dimensionless graphs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00872344
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 68
    Electronic Resource
    Electronic Resource
    Future groundwater conditions under long-term water stresses in an arid urban area (1994)
    Springer
    Water resources management 8 (1994), S. 245-264 
    Details
    ISSN: 1573-1650
    Keywords: groundwater ; hydrogeochemical investigation ; simulation ; urban area ; arid climate groundwater management ; conservation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract The urban area of Greater Dhahran has an extremely arid climate where the average annual rainfail is less than 71 mm. The Umm Er Radhuma (UER) aquifer in that area is the main source of domestic and landscape irrigation demands. Groudwater use has increased drastically during the last 15 years due to extensive developments in the area. Numerical simulation techiques and hydrogeochemical investigations were carried out to assess the effects of increasing pumping rates on the piezometric surface in the UER aquifer and to predict the future levels and quality of water under different pumping scenarios. A groundwater flow model was developed and calibrated for the area. The increase in the water extraction rate between 1967 and 1990 has resulted in a decline in the piezometric surface by about 4 m in the Dhahran area. The results of simulation investigations indicated that if the present trend of the groundwater withdrawal rate continues, the water level is expected to drop by an additional 2 and by the end of the year 2000, by an additional 6 m by the end of 2010. If the present increasing rate in groundwater withdrawal is reduced by 50%, the additional drawdown will also be reduced to about 1 and 2.5 m by the end of years 2000 and 2010, respectively. The average total dissolved solids (TDS) has increased from 2750 to 3545 mg/l between 1967 and 1990 and will continue to rise to 3922 and 4361 by the end of years 2000 and 2010, respectively. These original findings are important because they postulates the negative impacts of increasing groundwater pumping from an aquifer in an arid urban area on future groundwater levels and quality. Therefore, effective groundwater management and conservation schemes should be adopted to maintain the long-term productivity and quality of aquifers in the area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00872400
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 69
    Electronic Resource
    Electronic Resource
    C2 and C3 hydrocarbon gases associated with highly reducing conditions in groundwater (1999)
    Springer
    Biogeochemistry 47 (1999), S. 15-23 
    Details
    ISSN: 1573-515X
    Keywords: ethane ; groundwater ; methane ; propane ; redox ; soil gas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract This study investigates the presence and concentration of light hydrocarbon gases in soil vapor located immediately above the capillary fringe of a petroleum-contaminated aquifer. A correlation was observed for the linear regression plot of redox potential versus detectable C2+C3 alkane concentrations for a limited number of sampling points. C2+C3 alkanes were not detected at points were redox potentials in groundwater exceeded --260 millivolts. The predominance of methanogenic processes in this redox range, as well as the observed C2+C3 concentration ratios, suggest that ethane and propane gases in soil vapor may be biogenically produced as well as a result of volatilization from NAPL.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006147818047
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 70
    Electronic Resource
    Electronic Resource
    C2 and C3 hydrocarbon gases associated with highly reducing conditions in groundwater (1999)
    Springer
    Biogeochemistry 47 (1999), S. 15-23 
    Details
    ISSN: 1573-515X
    Keywords: ethane ; groundwater ; methane ; propane ; redox ; soil gas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract This study investigates the presence and concentration of light hydrocarbon gases in soil vapor located immediately above the capillary fringe of a petroleum-contaminated aquifer. A correlation was observed for the linear regression plot of redox potential versus detectable C2+C3 alkane concentrations for a limited number of sampling points. C2+C3 alkanes were not detected at points were redox potentials in groundwater exceeded -260 millivolts. The predominance of methanogenic processes in this redox range, as well as the observed C2+C3 concentration ratios, suggest that ethane and propane gases in soil vapor may be biogenically produced as well as a result of volatilization from NAPL.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00993094
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 71
    Electronic Resource
    Electronic Resource
    Transition probability-based indicator geostatistics (1996)
    Springer
    Mathematical geology 28 (1996), S. 453-476 
    Details
    ISSN: 1573-8868
    Keywords: cokriging ; cross-covariance ; cross-variogram ; kriging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Traditionally, spatial continuity models for indicator variables are developed by empirical curvefitting to the sample indicator (cross-) variogram. However, geologic data may be too sparse to permit a purely empirical approach, particularly in application to the subsurface. Techniques for model synthesis that integrate hard data and conceptual models therefore are needed. Interpretability is crucial. Compared with the indicator (cross-) variogram or indicator (cross-) covariance, the transition probability is more interpretable. Information on proportion, mean length, and juxtapositioning directly relates to the transition probability: asymmetry can be considered. Furthermore, the transition probability elucidates order relation conditions and readily formulates the indicator (co)kriging equations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02083656
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 72
    Electronic Resource
    Electronic Resource
    Solving the kriging problem by using the Gram-Schmidt orthogonalization (1991)
    Springer
    Mathematical geology 23 (1991), S. 111-118 
    Details
    ISSN: 1573-8868
    Keywords: Hilbert space ; projection theorem ; kriging ; Gram-Schmidt orthogonalization ; cost of calculations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract This paper presents an approach to solve the kriging problem, defined in terms of projections, by using Gram-Schmidt orthogonalization. The Gram-Schmidt orthogonalization allows us to find an optimal approximationY* in then-dimensional subspaceH n of any vectorY element of a Hilbert spaceH. This approach requiresO(n 3) multiplication operations to obtain an orthogonal basis, andO(n 2) multiplications needed to calculate kriging solution for a given point.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02065970
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 73
    Electronic Resource
    Electronic Resource
    Analysis and Estimation of Natural Processes with Nonhomogeneous Spatial Variation Using Secondary Information (1998)
    Springer
    Mathematical geology 30 (1998), S. 57-76 
    Details
    ISSN: 1573-8868
    Keywords: vector random fields ; generalized covariances ; permissibility criteria ; kriging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Natural processes encountered in mining, hydrogeologic, environmental, etc. applications usually are poorly known because of scarcity of data over the area of interest. Therefore, stochastic estimation techniques are the tool of choice for a careful accounting of the heterogeneity and uncertainty involved. Within such a framework, a better utilization of all available data concerning the process of interest and all other natural processes related to it, is of primary importance. Because many natural processes show complicated spatial trends, the hypothesis of spatial homogeneity cannot be invoked always, and the more general theory of intrinsic spatial random fields should be employed. Efficient use of secondary information in terms of the intrinsic model requires that suitable permissibility criteria for the generalized covariances and cross-covariances are satisfied. A set of permissibility criteria are presented for the situation of two intrinsic random fields. These criteria are more general and comprehensive than the ones currently available in the geostatistical literature. A constrained least-square technique is implemented for the inference of the generalized covariance and cross-covariance parameters, and a synthetic example is used to illustrate the methodology. The numerical results show that the use of secondary information can lead to significant reductions in the estimation errors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021761305044
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 74
    Electronic Resource
    Electronic Resource
    Short Note: Effective Hydraulic Conductivity and Transmissivity for Heterogeneous Aquifers (2000)
    Springer
    Mathematical geology 32 (2000), S. 751-759 
    Details
    ISSN: 1573-8868
    Keywords: groundwater ; upscaling ; effective hydraulic conductivity ; transmissivity ; stochastic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Regional scale models of groundwater flow and transport often employ domain discretizations with grid blocks larger than typical scales of field data. For heterogeneous formations, this difference in scales is often handled by using effective (upscaled) parameters. We investigate the problem of upscaling hydraulic conductivity and transmissivity from a small scale of measurement to a larger scale of grid blocks. Transmissivity statistics is expressed in terms of statistics of hydraulic conductivity, and expressions for the effective (upscaled) hydraulic conductivity K eff and transmissivity T eff for steady state flow in confined heterogeneous aquifers are derived by means of stochastic averaging and perturbation analysis. These expressions reveal that the commonly used relation T eff = BK eff, where B is the confined aquifer thickness, is not generally valid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007546607242
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 75
    Electronic Resource
    Electronic Resource
    Adding Local Accuracy to Direct Sequential Simulation (2000)
    Springer
    Mathematical geology 32 (2000), S. 815-850 
    Details
    ISSN: 1573-8868
    Keywords: sequential simulation ; kriging ; local vs. global accuracy ; bootstrap ; entropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Geostatistical simulations are globally accurate in the sense that they reproduce global statistics such as variograms and histograms. Kriging is locally accurate in the minimum local error variance sense. Building on the concept of direct sequential simulation, we propose a fast simulation method that can share these opposing objectives. It is shown that the multiple-point entropy of the resulting simulation is related to the univariate entropy of the local conditional distributions used to draw simulated values. Adding local accuracy to conditional simulations does not detract much from variogram reproduction and can be used to increase multiple-point entropy. The methods developed are illustrated using a case study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007596423578
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 76
    Electronic Resource
    Electronic Resource
    Adding bounds to kriging (1992)
    Springer
    Mathematical geology 24 (1992), S. 171-176 
    Details
    ISSN: 1573-8868
    Keywords: geostatistics ; kriging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The ordinary kriging interpolation algorithm is extended by the inclusion of explicit lower and upper bounds on the estimate. The associated estimation variance is written as the ordinary kriging variance plus a non-negative correction term.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00897030
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 77
    Electronic Resource
    Electronic Resource
    Finite-element method in modeling geologic transport processes (1976)
    Springer
    Mathematical geology 8 (1976), S. 43-56 
    Details
    ISSN: 1573-8868
    Keywords: finite-element method ; numerical analysis ; simulation ; geophysics ; groundwater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Deterministic mathematical modeling of complex geologic transport processes may require the use of odd boundary shapes, time dependency, and two or three dimensions. Under these circumstances the governing transport equations must be solved by numerical methods. For a number of transport phenomena a general form of the convective-dispersion equation can be employed. The solution of this equation for complicated problems can be solved readily by the finite-element method. Using quadrilateral isoparametric elements or triangular elements and a computational algorithm based on Galerkin's procedure, solutions to unsteady heat flux from a dike and seawater intrusion in an aquifer have been obtained. These examples illustrate that the finite-element numerical procedure is well suited for solving boundary-value problems resulting from modeling of complex physical phenomena.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01039684
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 78
    Electronic Resource
    Electronic Resource
    Quality mapping of the Ryytimaa dolomite in western Finland (1996)
    Springer
    Mathematical geology 28 (1996), S. 477-499 
    Details
    ISSN: 1573-8868
    Keywords: Fennoscandia ; kriging ; indicators ; indicator principal components simulation ; geostatistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The Ryytimaa dolomite formation in western Finland is mined for fertilizing purposes in agriculture. Ordinary kriging, indicator kriging, and indicator principal components simulation were used to map the dolomite quality. The fertilizing properties depend on the relative amounts of MgO and neutralizing CaO in dolomite. Based on the chemical composition the dolomite is divided into six quality classes according to the Finnish legislation. This quality classification is only partially in accordance with the three populations inferred from the distributions of the MgO, CaO, and neutralizing CaO contents. These populations probably represent compositionally different dolomite layers, now forming complicated fold interference structures that are visible on the kriged maps. The mapping of the quality, and thus, selective mining of the dolomite deposit is possible using the quality classification based on the three populations. In contrast, selective mining of the dolomite based on the legislation is difficult—at least with techniques used in this study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02083657
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 79
    Electronic Resource
    Electronic Resource
    On counting the number of data pairs for semivariogram estimation (1991)
    Springer
    Mathematical geology 23 (1991), S. 929-943 
    Details
    ISSN: 1573-8868
    Keywords: kriging ; multivariate Gaussian distribution ; regionalized variable ; sampling design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract In planning spatial sampling studies for the purpose of estimating the semivariogram, the number of data pairs separated by a given distance is sometimes used as a comparative index of the precision which can be expected from a given sampling design. Because spatial data are correlated, this index can be unreliable. An alternative index which partially corrects for this correlation, themaximum equivalent uncorrelated pairs, is proposed for comparing spatial designs. The index is developed under the assumption that the underlying stochastic process is Gaussian and is appropriate when the (population) semivariogram is to be estimated by the sample semivariogram.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02066733
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 80
    Electronic Resource
    Electronic Resource
    On the stability of the geostatistical method (1992)
    Springer
    Mathematical geology 24 (1992), S. 45-59 
    Details
    ISSN: 1573-8868
    Keywords: kriging ; mean squared prediction error ; resistance ; robustness ; spatial dependence ; spatial prediction ; trend ; variogram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract A thorough geostatistical analysis of spatial data, observed at given spatial locations, includes exploratory data analysis, spatial-model building, diagnosing the model fit, and inference on unknown model parameters or unobserved values (at known locations). Using results from mathematical analysis, exact and asymptotic distribution theory, and simulation studies, we argue that, when used sensibly, the geostatistical method is reassuringly stable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00890087
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 81
    Electronic Resource
    Electronic Resource
    Correcting the Smoothing Effect of Estimators: A Spectral Postprocessor (2000)
    Springer
    Mathematical geology 32 (2000), S. 787-813 
    Details
    ISSN: 1573-8868
    Keywords: local accuracy ; conditional bias ; spectral amplitudes ; kriging ; stochastic simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The postprocessing algorithm introduced by Yao for imposing the spectral amplitudes of a target covariance model is shown to be efficient in correcting the smoothing effect of estimation maps, whether obtained by kriging or any other interpolation technique. As opposed to stochastic simulation, Yao's algorithm yields a unique map starting from an original, typically smooth, estimation map. Most importantly it is shown that reproduction of a covariance/semivariogram model (global accuracy) is necessarily obtained at the cost of local accuracy reduction and increase in conditional bias. When working on one location at a time, kriging remains the most accurate (in the least squared error sense) estimator. However, kriging estimates should only be listed, not mapped, since they do not reflect the correct (target) spatial autocorrelation. This mismatch in spatial autocorrelation can be corrected via stochastic simulation, or can be imposed a posteriori via Yao's algorithm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007544406740
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 82
    Electronic Resource
    Electronic Resource
    Efficient updating of kriging estimates and variances (1992)
    Springer
    Mathematical geology 24 (1992), S. 129-133 
    Details
    ISSN: 1573-8868
    Keywords: geostatistics ; kriging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract This short note presents a method for efficiently updating ordinary kriging estimates and variances when one or more additional samples are incorporated into the kriging system. First, the foundation linear algebra result is presented. Then the update equations are derived. Finally, an illustrative application of updating is briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00890091
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 83
    Electronic Resource
    Electronic Resource
    Variograms and their role in interpretation of soft iron ore types (1977)
    Springer
    Mathematical geology 9 (1977), S. 99-110 
    Details
    ISSN: 1573-8868
    Keywords: autocorrelation ; kriging ; mineral exploration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Difficulties are encountered in the interpretation of variograms from mixed populations. A case history study of a soft iron ore body capped by laterite demonstrates that the variations observed in variograms for different elements are caused mainly by intermixing of different lithologic units which are interstratified. In the case of soft iron ore, occasional bands of clay and blue dust affect significantly the variations observed for iron, silicon, and aluminum. In the future, it is recommended that the variograms produced reflect a single population.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02312498
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 84
    Electronic Resource
    Electronic Resource
    Kriging in terms of projections (1977)
    Springer
    Mathematical geology 9 (1977), S. 563-586 
    Details
    ISSN: 1573-8868
    Keywords: kriging ; geostatistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract In the last few years, an increasing number of practical studies using so-called kriging estimation procedures have been published. Various terms, such as universal kriging, lognormal kriging, ordinary kriging, etc., are used to define different estimation procedures, leaving a certain confusion about what kriging really is. The object of this paper is to show what is the common backbone of all these estimation procedures, thus justifying the common name of kriging procedures. The word “kriging” (in French “krigeage”) is a concise and convenient term to designate the classical procedure of selecting, within agiven class of possible estimators, the estimator with a minimum estimation variance (i.e., the estimator which leads to a minimum variance of the resulting estimation error). This estimation variance can be seen as a squared distance between the unknown value and its estimator; the process of minimization of this distance can then be seen as the projection of the unknown value onto the space within which the search for an estimator is carried out.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02067214
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 85
    Electronic Resource
    Electronic Resource
    A fast method for the solution of a system of simultaneous linear equations—A method adapted to a particular problem (1978)
    Springer
    Mathematical geology 10 (1978), S. 369-374 
    Details
    ISSN: 1573-8868
    Keywords: linear equations ; kriging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract In mineral deposit evaluation, the estimation of block values can involve the solution of as many as 100,000 systems of linear equations. To minimize computing costs it is important that the program to solve the linear systems be as efficient as possible. Standard library routines tend to contain very general stable methods using pivoting and iteration to ensure high accuracy solutions. Here, a particular method has been developed that gives a substantial improvement in run time at the occasional expense of accuracy and stability. The method is not new—just a simple application of Gaussian elimination in the symmetric case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01031741
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 86
    Electronic Resource
    Electronic Resource
    Robust estimation of the variogram: I (1980)
    Springer
    Mathematical geology 12 (1980), S. 115-125 
    Details
    ISSN: 1573-8868
    Keywords: Geostatistics ; kriging ; robust estimation ; variogram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract It is a matter of common experience that ore values often do not follow the normal (or lognormal) distributions assumed for them, but, instead, follow some other heavier-tailed distribution. In this paper we discuss the robust estimation of the variogram when the distribution is normal-like in the central region but heavier than normal in the tails. It is shown that the use of a fourth-root transformation with or without the use of M-estimation yields stable robust estimates of the variogram.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01035243
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 87
    Electronic Resource
    Electronic Resource
    Normal and lognormal estimation (1979)
    Springer
    Mathematical geology 11 (1979), S. 407-422 
    Details
    ISSN: 1573-8868
    Keywords: conditional expectation ; kriging ; linear estimation ; normal estimation ; lognormal estimation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract A comprehensive theoretical study of the problem of estimation of regionalized variables with normal or lognormal distribution is presented. Unbiased linear estimators are derived, under both assumptions that the population mean is known and unknown, and their error variance is calculated. The minimum variance kriging estimators are studied in more detail and are compared with the conditional expectations. The emphasis is on the study of lognormally distributed variates. The derived mathematical formulas are applicable to the optimal contouring of sample values with the appropriate distribution, as well as the optimal estimation of blocks of ore in mineral deposits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01029297
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 88
    Electronic Resource
    Electronic Resource
    Geostatistical estimation of parameters for hydrologic transport modeling (1981)
    Springer
    Mathematical geology 13 (1981), S. 415-428 
    Details
    ISSN: 1573-8868
    Keywords: geostatistics ; hydrologic transport ; kriging ; radioactive waste disposal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract A significant part of the work of evaluating a geologic formation as a potential repository for hazardous wastes is the modeling of contaminant transport in the surrounding media in the event the repository is breached. The transport equations that are commonly used are deterministic functions. However, because the data can vary within the area being considered, there is a degree of uncertainty associated with the results obtained from the contaminant transport models. There are several ways to incorporate uncertainties into the transport equations, but they assume that distributions and parameters such as variances and covariances are known. This paper discusses the application of geostatistical spatial estimation techniques to estimate quantities used in transport modeling. The techniques are illustrated on data from an electric analog simulation of a two-dimensional ground water system. Geostatistical methods were used to estimate potential and hydraulic conductivity surfaces from data generated from the simulation of the ground water system. Although the two surfaces were highly dependent through Darcy's Law, they were estimated independently. Independent verification of the two surfaces showed that they approximately satisfied the required conservation of mass condition that: ∇ ⋅ v = 0.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01079645
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 89
    Electronic Resource
    Electronic Resource
    Geostatistical case studies of the advantages of lognormal-de Wijsian kriging with mean for a base metal mine and a gold mine (1982)
    Springer
    Mathematical geology 14 (1982), S. 547-555 
    Details
    ISSN: 1573-8868
    Keywords: geostatistics ; kriging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Parallel variogram analyses, block kriging, and follow-up studies were effected for the lead content of part of the Prieska copper-zinc ore body and for the gold content of the highly variable Breef in a section of the Loraine gold mine, based first on untransformed values and second on logarithmically transformed values using the lognormal-de Wijsian model. For both models the effect was also analyzed of using the population mean or ignoring it. Practical follow-up comparisons confirm theoretical considerations and show that on these mines conditional biases can be eliminated conveniently by kriging with mean; also that the lognormal-de Wijsian model with mean gives the best results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01033878
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 90
    Electronic Resource
    Electronic Resource
    Two methods with different objectives: Splines and kriging (1983)
    Springer
    Mathematical geology 15 (1983), S. 245-257 
    Details
    ISSN: 1573-8868
    Keywords: kriging ; splines ; measurement errors ; generalized covariance ; structural identification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract When drawing a contour map from a set of irregularly spaced data points, two methods are often used: The first corresponds to a rather aesthetic criterion and consists of obtaining contour lines which will be as “smooth”as possible and will honor the data points. This generally is the objective of the draftsman, and it can be automatically performed by the method of spline interpolation. The other method, used in kriging, is to compute the Best Linear Unbiased Estimator (B.L.U.E.),that is, to obtain a map as accurate as possible. Is it possible, in practice, to predict whether the aesthetic map will also be accurate? In this paper, we first examine the theoretical point of view: Spline interpolation is equivalent to kriging with a given (generalized)covariance. We then take an example to show how this question can be answered in practice: by testing how well the spline covariance is suited to the data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01036069
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 91
    Electronic Resource
    Electronic Resource
    Integration of mineral resource data for Kasmere Lake area, Northwest Manitoba, with emphasis on uranium (1983)
    Springer
    Mathematical geology 15 (1983), S. 25-45 
    Details
    ISSN: 1573-8868
    Keywords: Discriminant analysis ; autocorrelation ; kriging ; multiple regression ; uranium ; mineral resources
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Geological and geophysical data digitized by Fabbri (1981)are augmented by eleven lakesediment geochemical variables in a quantitative study of the Kasmere Lake—Whiskey Jack Lake area, NW Manitoba. Each of 33 geological map units (Archean and Aphebian igneous and metamorphic rocks)have a fairly distinct multivariate geochemical and geophysical signal, as shown by discriminant analysis which is able to “recover” the geological map from the geophysical and geochemical data. Autocorrelation analysis of the geochemical variables, after removing a quadratic trend, indicate that copper, nickel, uranium, and cobait have a zone of influence from 15 to 30 km or more, with a marked anisotropy parallel to geological, geophysical, and structural trends which run NE-SW, parallel to the Wollaston fold belt. The observed uranium autocorrelation coefficients are modeled as a two-dimensional exponential function with elliptical contours. A trend-signal-noise model is applied to the lake-sediment uranium using kriging on residuals from the quadratic trend. A map comparing the resulting lake-sediment uranium signal with radiometric uranium/thorium patterns indicates considerable overlap and a generally good prediction of known uranium occurrences. In areas with a strong lake-sediment uranium signal, Aphebian metasediments have a somewhat different multivariate geochemical character from Archean and Hudsonian igneous and metamorphic rocks, suggesting a method of removing areas from the signal underlain by granites that may be economically uninteresting. Logistic and stepwise regression experiments based on a control area which includes most of the presently reported occurrences are used to predict areas favorable for uranium exploration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01030074
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 92
    Electronic Resource
    Electronic Resource
    Kriging in a global neighborhood (1984)
    Springer
    Mathematical geology 16 (1984), S. 249-265 
    Details
    ISSN: 1573-8868
    Keywords: kriging ; moving neighborhood ; global neighborhood ; geostatistics ; automatic contouring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The kriging estimator is usually computed in a moving neighborhood; only the data near the point to be estimated are used. This moving neighborhood approach creates discontinuities in mapping applications. An alternative approach is presented here, whereby all points are estimated using all the available data. To solve the resulting large linear system the kriging estimator is expressed in terms of the inverse of the covariance matrix. The covariance matrix has the advantage of being positive definite and the size of system which can be solved without encountering numerical instability is substantially increased. Because the kriging matrix does not change, the estimator can be written in terms of scalar products, thus avoiding the more time-consuming matrix multiplications of the standard approach. In the particular case of a covariance which is zero for distances greater than a fixed value (the range), the resulting banded structure of the covariance matrix is shown to lead to substantial computational savings in both run time and storage space. In this case the calculation time for the kriging variance is also substantially reduced. The present method is extended to the nonstationary case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01032690
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 93
    Electronic Resource
    Electronic Resource
    Application of fuzzy clustering and fuzzy classification to evaluate the provenance of glacial till (1984)
    Springer
    Mathematical geology 16 (1984), S. 283-301 
    Details
    ISSN: 1573-8868
    Keywords: Bayesian classifiers ; classification ; cluster analysis ; cluster validity ; fuzzyc means ; fuzzyc varieties ; fuzzy covariances ; geochemical prospecting ; glacial till ; kriging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract To evaluate the provenance of glacial till, the trace element content of magnetite was used. Magnetite was present in all known rock types and all till samples in the area investigated. By using fuzzy-set theory it was possible to group samples of magnetite taken from bedrock into relatively homogeneous and geologically meaningful groups and also, by fuzzy classification, to relate the till samples to the rocks in such a way that the relative contribution of each rock type to the till is estimated. Each rock and till sample is assigned a membership value between 0 and 1 for each rock type. The membership values, for a certain rock type in the till, are then interpolated by kriging onto maps. Magnetites from skarns associated with sulfide ores especially are rather distinct, and so a map of such membership values for till unveils all known ore deposits some 1–5 km “downstream”in the general direction of the ice flow. Other anomalies show up which cannot be related to hitherto known ores or mineralizations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01032692
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 94
    Electronic Resource
    Electronic Resource
    Robustness of variograms and conditioning of kriging matrices (1984)
    Springer
    Mathematical geology 16 (1984), S. 809-822 
    Details
    ISSN: 1573-8868
    Keywords: variogram ; robustness ; kriging ; conditioning number
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Current ideas of robustness in geostatistics concentrate upon estimation of the experimental variogram. However, predictive algorithms can be very sensitive to small perturbations in data or in the variogram model as well. To quantify this notion of robustness, nearness of variogram models is defined. Closeness of two variogram models is reflected in the sensitivity of their corresponding kriging estimators. The condition number of kriging matrices is shown to play a central role. Various examples are given. The ideas are used to analyze more complex universal kriging systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01036706
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 95
    Electronic Resource
    Electronic Resource
    Fitting variogram models by weighted least squares (1985)
    Springer
    Mathematical geology 17 (1985), S. 563-586 
    Details
    ISSN: 1573-8868
    Keywords: generalized least squares ; kriging ; median polish ; robustness ; stationarity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The method of weighted least squares is shown to be an appropriate way of fitting variogram models. The weighting scheme automatically gives most weight to early lags and down-weights those lags with a small number of pairs. Although weights are derived assuming the data are Gaussian (normal), they are shown to be still appropriate in the setting where data are a (smooth) transform of the Gaussian case. The method of (iterated) generalized least squares, which takes into account correlation between variogram estimators at different lags, offer more statistical efficiency at the price of more complexity. Weighted least squares for the robust estimator, based on square root differences, is less of a compromise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01032109
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 96
    Electronic Resource
    Electronic Resource
    Determination of support in soil sampling (1986)
    Springer
    Mathematical geology 18 (1986), S. 529-537 
    Details
    ISSN: 1573-8868
    Keywords: geostatistics ; kriging ; nugget effect ; soil sampling ; support
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Short-range variation of measurements of a soil characteristic is a function of the support (i.e., size, shape, and orientation of the physical sample taken at a sample point) of the soil samples. This short-range variance often shows up as a substantial component of the “nugget effect” in experimental semivariograms or estimated generalized covariance functions. Proper choice of support may substantially reduce short-range variance (or nugget) of measurements made at sample points and thereby reduce estimation variance in point or block kriging based on these measurements. Appropriate variance formulas and an example are given for determination of support when support is an array of vertical cores (or bucket auger samples) of equal depth and diameter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00914253
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 97
    Electronic Resource
    Electronic Resource
    Matheronian geostatistics—Quo vadis? (1986)
    Springer
    Mathematical geology 18 (1986), S. 93-117 
    Details
    ISSN: 1573-8868
    Keywords: deterministic ; “estimation variance” ; interpolation ; geostatistics ; kriging ; least-squares prediction ; ore deposit assessment ; probabilistic ; semivariogram ; statistical inference
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Components of geostatistical estimation, developed as a method for ore deposit assessment, are discussed in detail. The assumption that spatial observations can be treated as a stochastic process is judged to be an inappropriate model for natural data. Problems of semivariogram formulation are reviewed, and this method is considered to be inadequate for estimating the function being sought. Characteristics of bivariate interpolation are summarized, highlighting kriging limitations as an interpolation method. Limitations are similar to those of inverse distance weighted observations interpolation. Attention is drawn to the local bias of kriging and misplaced claims that it is an “optimal” interpolation method. The so-called “estimation variance,” interpreted as providing confidence limits for estimation of mining blocks, is shown to be meaningless as an index of local variation. The claim that geostatistics constitutes a “new science” is examined in detail. Such novelties as exist in the method are shown to transgress accepted principles of scientific inference. Stochastic modeling in general is discussed, and purposes of the approach emphasized. For the purpose of detailed quantitative assessment it can provide only prediction qualified by hypothesis at best. Such an approach should play no part in ore deposit assessment where the need is for local detailed inventories; these can only be achieved properly through local deterministic methods, where prediction is purely deductive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00897657
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 98
    Electronic Resource
    Electronic Resource
    An application of disjunctive kriging for earthquake ground motion estimation (1986)
    Springer
    Mathematical geology 18 (1986), S. 197-213 
    Details
    ISSN: 1573-8868
    Keywords: disjunctive kriging ; nonlinear geostatistics ; kriging ; earthquake ground motion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract For earthquake ground motion studies, the actual ground motion distribution should be reproduced as accurately as possible. For optimal estimation of ground motion, kriging has been shown to provide accurate estimates. Although kriging is accurate for this application, some estimates it provides are underestimates. This has dire consequences for subsequent design for earthquake resistance. Kriging does not provide enough information to allow an analysis of each estimate for underestimation. For such an application, disjunctive kriging is better applied. This advanced technique quantifies the probability that an estimate equals or exceeds particular levels of ground motion. Furthermore, disjunctive kriging can provide improved estimation accuracy when applied for local estimation of ground motion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00898283
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 99
    Electronic Resource
    Electronic Resource
    A parametric study of robustness of kriging variance as a function of range and relative nugget effect for a spherical semivariogram (1986)
    Springer
    Mathematical geology 18 (1986), S. 477-488 
    Details
    ISSN: 1573-8868
    Keywords: kriging ; nugget effect ; range ; semivariogram ; geostatistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract In geostatistics, an estimation of blocks of a deposit is reported along with the variance of error made in their estimation. This calculation is based on the model chosen for the semivariogram of the deposit so that mistakes in its estimation can manifest themselves in the perception of accuracy with which blocks are known. Changes in kriging variance resulting from various amounts of error in modeling the relative nugget effect and range of the semivariogram are investigated for an extensive set of spherical semivariograms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00897500
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 100
    Electronic Resource
    Electronic Resource
    Random vectors and spatial analysis by geostatistics for geotechnical applications (1987)
    Springer
    Mathematical geology 19 (1987), S. 467-479 
    Details
    ISSN: 1573-8868
    Keywords: random vectors ; spatial analysis ; vector variogram ; kriging ; rock fracture orientation ; structural modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Geostatistics is extended to the spatial analysis of vector variables by defining the estimation variance and vector variogram in terms of the magnitude of difference vectors. Many random variables in geotechnology are in vectorial terms rather than scalars, and its structural analysis requires those sample variable interpolations to construct and characterize structural models. A better local estimator will result in greater quality of input models; geostatistics can provide such estimators: kriging estimators. The efficiency of geostatistics for vector variables is demonstrated in a case study of rock joint orientations in geological formations. The positive cross-validation encourages application of geostatistics to spatial analysis of random vectors in geoscience as well as various geotechnical fields including optimum site characterization, rock mechanics for mining and civil structures, cavability analysis of block cavings, petroleum engineering, and hydrologic and hydraulic modelings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00896915
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...