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  • Articles  (26)
  • geostatistics  (26)
  • 1990-1994  (26)
  • Geosciences  (26)
  • Economics
  • Technology
  • 1
    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
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  • 2
    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
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  • 3
    Electronic Resource
    Electronic Resource
    On the geologic structure of the Explora Escarpment (Weddell Sea, Antarctica) revealed by satellite and Shipboard data evaluation (1994)
    Springer
    Marine geophysical researches 16 (1994), S. 325-345 
    Details
    ISSN: 1573-0581
    Keywords: Bathymetry ; gravity ; magnetics ; satellite data ; Gondwana breakup ; geostatistics ; geophysical inverse theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Bathymetric, gravity, and magnetic data from Antarctic expeditions with RV POLARSTERN and satellite altimeter data from the Geosat Geodetic Mission are analysed using methods from geostatistics and geophysical inverse theory. The Explora Escarpment represents the edge between the Antarctic Continental Shelf and the Weddell Abyssal Plain. It is an important link in the reconstruction of Gondwana breakup, but a feature as large as the 2000 m deep Wegener Canyon was only discovered in 1984, when extensive bathymetric, gravimetric, and magnetic surveys with RV POLARSTERN began. Geostatistics, the theory of regionalized variables, is applied to integrate dense surveys of Wegener Canyon and sparse observations in adjacent areas into maps with full coverage of the 230 km by 330 km area at 10°–20° W/70°–72° S. The resultant highresolution bathymetric and gravity maps reveal detailed structures of the Explora Escarpment. Using geophysical inversion, the gravity terrain effect is calculated. Satellite data are used for their better coverage, but have much lower resolution. Nevertheless, the structures of Wegener Canyon and other more prominent features appear with surprisingly good correlation also in the Geosat altimeter data. While it was initially supposed that Wegener Canyon is purely an erosional structure, the magnetic map now provides evidence of the ‘canyon's’ tectonic origin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01203971
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  • 4
    Electronic Resource
    Electronic Resource
    Variance as a function of sample support size (1990)
    Springer
    Mathematical geology 22 (1990), S. 107-121 
    Details
    ISSN: 1573-8868
    Keywords: Variogram ; geostatistics ; sample support ; variance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The effect of sample support size on variance is examined and evaluated. Results based on variograms and geostatistics are compared to the classical relationship developed by H. F. Smith in 1938; that is, that the variance is reduced fromV 1 toV 1 /n b as the support area increases from I ton plots for uniformity trials. The exponentb is between zero and one. Theoretical results are based on use of auxiliary functions and account for the size and shape of the sample support and the overall field geometry. Results are given in terms of approximations by rational functions for ease of calculation. Experimental results for uniformity trials, infiltration measurements, and spectral data from satellites are compared to theoretical and empirical results. Applications include not only uniformity trials, but also measurement theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00890300
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  • 5
    Electronic Resource
    Electronic Resource
    Comparing some approximate methods for building local confidence intervals for predicting regionalized variables (1990)
    Springer
    Mathematical geology 22 (1990), S. 123-144 
    Details
    ISSN: 1573-8868
    Keywords: nonlinear estimators ; geostatistics ; confidence intervals ; indicator kriging ; probability kriging ; disjunctive kriging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Approximate local confidence intervals can be produced by nonlinear methods designed to estimate indicator variables. The most precise of these methods, the conditional expectation, can only be used in practice in the multi-Gaussian context. Theoretically, less efficient methods have to be used in more general cases. The methods considered here are indicator kriging, probability kriging (indicator-rank co-kriging), and disjunctive kriging (indicator co-kriging). The properties of these estimators are studied in this paper in the multi-Gaussian context, for this allows a more detailed study than under more general models. Conditional distribution approximation is first studied. Exact results are given for mean squared errors and conditional bias. Then conditional quantile estimators are compared empirically. Finally, confidence intervals are compared from the points of view of bias and precision.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00890301
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  • 6
    Electronic Resource
    Electronic Resource
    Regionalization in geology by multivariate classification (1990)
    Springer
    Mathematical geology 22 (1990), S. 573-588 
    Details
    ISSN: 1573-8868
    Keywords: classification ; regionalization ; Bayes' theorem ; geostatistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The concept of multivariate classification of “geological objects” can be combined with the concept of regionalized variables to yield a procedure for typification of geological objects, such as rock units, well records, or samples. Numerical classification is followed by subdivision of the area of investigation, and culminates in a regionalization or mapping of the classification onto the plane. Regions are subdivisions of the map area which are spatially contiguous and relatively homogeneous in their geological properties. The probability of correct classification of each point within a region as being part of that region can be assessed in terms of Bayesian probability as a space-dependent function. The procedure is applied to subsurface data from western Kansas. The geologic properties used are quantitative variables, and relationships are expressed by Mahalanobis' distances. These functions could be replaced by other metrics if qualitative or binary data derived from geological descriptions or appraisals were included in the analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00890505
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  • 7
    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
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  • 8
    Electronic Resource
    Electronic Resource
    A Bayesian/maximum-entropy view to the spatial estimation problem (1990)
    Springer
    Mathematical geology 22 (1990), S. 763-777 
    Details
    ISSN: 1573-8868
    Keywords: spatial estimation ; entropy ; Bayes law ; information ; geostatistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The purpose of this paper is to stress the importance of a Bayesian/maximum-entropy view toward the spatial estimation problem. According to this view, the estimation equations emerge through a process that balances two requirements: High prior information about the spatial variability and high posterior probability about the estimated map. The first requirement uses a variety of sources of prior information and involves the maximization of an entropy function. The second requirement leads to the maximization of a so-called Bayes function. Certain fundamental results and attractive features of the proposed approach in the context of the random field theory are discussed, and a systematic spatial estimation scheme is presented. The latter satisfies a variety of useful properties beyond those implied by the traditional stochastic estimation methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00890661
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  • 9
    Electronic Resource
    Electronic Resource
    Interrelations between geostatistics and information theory and their practical use (1991)
    Springer
    Mathematical geology 23 (1991), S. 3-7 
    Details
    ISSN: 1573-8868
    Keywords: geostatistics ; information theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Well-defined analytical interrelations exist between the geostatistical estimation variance performing an expression of degree of geological exploration and the task-oriented entropy as a concept of information theory. The example of normal distribution shows that this relationship can be expressed in mathematical terms. An extensive practical use could consist in the improvement of exploration optimization on the common basis of continuous geological parameters as is demonstrated by means of an example.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02065960
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  • 10
    Electronic Resource
    Electronic Resource
    Estimation of covariance parameters in kriging via restricted maximum likelihood (1991)
    Springer
    Mathematical geology 23 (1991), S. 119-135 
    Details
    ISSN: 1573-8868
    Keywords: Gaussian random field ; covariance estimation ; geostatistics ; eigenvalue decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract In kriging, parametric approaches to covariance (or variogram) estimation require that unknown parameters be inferred from a single realization of the underlying random field. An approach to such an estimation problem is to assume the field to be Gaussian and iteratively minimize a (restricted) negative loglikelihood over the parameter space. In doing so, the associated computational burden can be considerable. Also, it is usually not easy to check whether or not the minimum achieved is global. In this note, we show that in many practical cases, the structure of the covariance (or variogram) function can be exploited so that iterative minimizing algorithms may be advantageously replaced by a procedure that requires the computation of the roots of a simple rational function and the search for the minimum of a function depending on one variable only. As a consequence, our approach allows one to observe in a straightforward fashion the presence of local minima. Furthermore, it is shown that insensitivity of the likelihood function to changes in parameter value can be easily detected. The note concludes with numerical simulations that illustrate some key features of our estimation procedure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02065971
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