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  • 1
    Series available for loan
    Series available for loan
    Methods for the regional gravity field modelling from SST and SGG data (1990)
    Helsinki
    Associated volumes
    Details Availability
    Call number: S 90.0085(90,2)
    In: Reports of the Finnish Geodetic Institute
    Type of Medium: Series available for loan
    Pages: 17 S.
    ISBN: 9517111339
    Series Statement: Reports of the Finnish Geodetic Institute 90,2
    Language: English
    Location: Lower compact magazine
    Branch Library: GFZ Library
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  • 2
    Electronic Resource
    Electronic Resource
    Production and cytogenetics of tetraploid–octoploid Avena hybrids (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 114 (1995), S. 0 
    Details
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The objectives of this research were to gather hybridization information about crosses between tetraploid and synthetically derived octoploid lines of Avena and their reciprocals, and to study the cytology of the hybrids obtained. When the octoploid plants were used as females, only 2.6% of the pollinated florets set seed, while seed set increased to 39.0% in reciprocal crosses. However, germination was 95.7% for the first group of hybrids and only 18.2% for the reciprocals. These diverse results can be explained by the paternal: maternal endosperm genomic ratios and the hypothesis of polar nuclei activation. The tetraploid-octoploid hybrids did not always contain 42 chromosomes. Octoploid lines derived indirectly from tetraploid (AABB) × hexaploid (AACCDD) crosses were found to retain their A and B genome chromosomes. Univalents in the above hybrids averaged 15.44 in 1990 and 15.15 in 1991, indicating the presence of C and D genome chromosomes inherited from the octoploid lines. Directly synthesized octoploids from diploid (AcAc) × hexaploid (AACCDD) crosses were found to form 20.44 univalents, 5.30 bivalents, and 2.69 trivalents when crossed with AABB tetraploid species. The high number of univalents indicates that chromosomes from at least three genomes, i.e. B, C, and D, remain unpaired, while trivalents are the result of homology between the A and Ac genomes. Hybrids between tetraploid and octoploid lines can be obtained at low frequencies but, regardless of the direction of the cross, these hybrids are highly sterile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1439-0523.1995.tb00778.x
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  • 3
    Electronic Resource
    Electronic Resource
    The use of FFT techniques in physical geodesy (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 100 (1990), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The fast Fourier transform (FFT) technique is a very powerful tool for the efficient evaluation of gravity field convolution integrals. It can handle heterogeneous and noisy data, and thus presents a very attractive alternative to the classical, time consuming approaches, provided gridded data are available. This paper reviews the mathematics of the FFT methods as well as their practical problems, and presents examples from physical geodesy where the application of these methods is especially advantageous. The spectral evaluation of Stokes’, Vening Meinesz' and Molodensky's integrals, least-squares collocation in the frequency domain, integrals for terrain reductions and for airborne gravity gradiometry, and the computation of covariance and power spectral density functions are treated in detail. Numerical examples illustrate the efficiency and accuracy of the FFT methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1990.tb00701.x
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  • 4
    Electronic Resource
    Electronic Resource
    How to handle topography in practical geoid determination: three examples (2000)
    Springer
    Journal of geodesy 74 (2000), S. 458-466 
    Details
    ISSN: 1432-1394
    Keywords: Key words: Terrain effects – Indirect effects – RTM – Helmert – Gravity – Geoid – GPS/levelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract.  Three different methods of handling topography in geoid determination were investigated. The first two methods employ the residual terrain model (RTM) remove–restore technique, yielding the quasigeoid, whereas the third method uses the classical Helmert condensation method, yielding the geoid. All three methods were used with the geopotential model Earth Gravity Model (1996) (EGM96) as a reference, and the results were compared to precise global positioning system (GPS) levelling networks in Scandinavia. An investigation of the Helmert method, focusing on the different types of indirect effects and their effects on the geoid, was also carried out. The three different methods used produce almost identical results at the 5-cm level, when compared to the GPS levelling networks. However, small systematic differences existed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001900000107
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  • 5
    Electronic Resource
    Electronic Resource
    A comparison of stable platform and strapdown airborne gravity (2000)
    Springer
    Journal of geodesy 74 (2000), S. 383-389 
    Details
    ISSN: 1432-1394
    Keywords: Key words: Airborne gravimetry ; Strapdown gravity system ; Analysis of flight tests ; DGPS/INS integration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract. To date, operational airborne gravity results have been obtained using either a damped two-axis stable platform gravimeter system such as the LaCoste and Romberg (LCR) S-model marine gravimeter or a strapdown inertial navigation system (INS), showing comparable accuracies. In June 1998 three flight tests were undertaken which tested an LCR gravimeter and a strapdown INS gravity system side by side. To the authors' knowledge, this was the first time such a comparison flight was undertaken. The flights occurred in Disko Bay, off the west coast of Greenland. Several of the flight lines were partly flown along existing shipborne gravity profiles to allow for an independent source of comparison of the results. The results and analysis of these flight tests are presented. The measurement method and error models for both the stable platform and strapdown INS gravity systems are presented and contrasted. An intercomparison of gravity estimates from both systems is given, along with a comparison of the individual estimates with existing shipborne gravity profiles. The results of the flight tests show that the gravity estimates from the two systems agree at the 2–3 mGal level, after the removal of a linear bias. This is near the combined noise level of the two systems. It appears that a combination of both systems would provide an ideal airborne gravity survey system, combining the excellent bias stability of the LCR gravimeter with the higher dynamic range and increased spatial resolution of the strapdown INS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001900000082
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  • 6
    Electronic Resource
    Electronic Resource
    Geoid models around Sognefjord using depth data (1998)
    Springer
    Journal of geodesy 72 (1998), S. 547-556 
    Details
    ISSN: 1432-1394
    Keywords: Key words. Bathymetry ; Gravity ; Terrain effects ; Quasigeoid minus geoid ; Geoid ; GPS/levelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract. Bathymetry data from Sognefjord, Norway, have been included in a terrain model, and their influence on the geoid has been calculated. The test area, located in the western part of Norway, was chosen due to its deep fjords and high mountains. Inclusion of bathymetry data in the terrain model altered the computed gravimetric geoid by as much as a few decimeters. The effect was detectable to a distance of more than 100 km. All calculated geoids, both with and without bathymetry data in the terrain model, fit the geoidal heights determined by available Global Positioning System (GPS) and levelling heights at the sub-decimetre level. Contrary to expectations, the accuracy in geoid prediction was reduced when using bathymetric data. The geoid changes were largest over the fjord where no GPS points were located. Different methods on the same area [isostatic and Residual Terrain Model (RTM)-terrain reductions] showed differences of approximately 1 m. Rigorous distinction between quasigeoid and geoid was found to be essential in this kind of area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001900050193
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  • 7
    Electronic Resource
    Electronic Resource
    Harmonic continuation and gridding effects on geoid height prediction (1992)
    Springer
    Journal of geodesy 66 (1992), S. 41-53 
    Details
    ISSN: 1432-1394
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract Least-squares collocation and Stokes integral formula, as implemented using the Fast Fourier Technique, handle the harmonic downward continuation problem quite differently. FFT furthermore requires gridded data, amplifying the difference of methods. We have in this paper studied numerically the effects of downward continuation and gridding in a mountainous area in central Norway. Topographically smoothed data were used in order to reduce these effects. Despite the smoothing, it was found that the vertical gravity gradient had values up to -11 mgal/km. The corresponding differences between geoid heights and the height anomalies at altitude reached 12 cm. The differences between geoid heights obtained using collocation or FFT with gravity data at terrain level or sea level showed differences between the values of up to 10 cm r.m.s. A part of this difference was a consequence of different data areas used in the FFT and collocation solution, though. Major discrepancies between the solutions were found in areas where the topographic smoothing could not be applied (deep fjords with no depth information in the used DTM) or where there seemed to be gross errors in the data. We conclude that proper handling of harmonic continuation is important, even when we as here have used a 1 km resolution DTM for the calculation of topographic effects. The effect of data gridding, required for the FFT method, seems not to be as serious as the need to limit the data distribution area, required when least squares collocation is used with randomly distributed data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806809
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  • 8
    Electronic Resource
    Electronic Resource
    Airborne gravimetry used in precise geoid computations by ring integration (1998)
    Springer
    Journal of geodesy 72 (1998), S. 600-605 
    Details
    ISSN: 1432-1394
    Keywords: Key words. Airborne gravimetry ; Gravity field extension ; Geoid computation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract. Two detailed geoids have been computed in the region of North Jutland. The first computation used marine data in the offshore areas. For the second computation the marine data set was replaced by the sparser airborne gravity data resulting from the AGMASCO campaign of September 1996. The results of comparisons of the geoid heights at on-shore geometric control showed that the geoid heights computed from the airborne gravity data matched in precision those computed using the marine data, supporting the view that airborne techniques have enormous potential for mapping those unsurveyed areas between the land-based data and the off-shore marine or altimetrically derived data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001900050198
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  • 9
    Electronic Resource
    Electronic Resource
    Endosperm Balance Number and the polar-nuclei activation hypotheses for endosperm development in interspecific crosses of Solanaceae and Gramineae, respectively (1995)
    Springer
    Theoretical and applied genetics 91 (1995), S. 848-855 
    Details
    ISSN: 1432-2242
    Keywords: Endosperm development ; Evolution ; Imprinting ; Incompatibility ; Reciprocal crosses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Endosperm Balance Number (EBN) and the polar-nuclei activation (PNA) hypotheses have been developed to interpret, explain and predict interspecific and interploidy crossabilities in the Solanums and the Gramineae, respectively. Although these two hypotheses evolved independently, they share a number of common features. Assignment of EBNs and ‘activation/response values’ (AVs/RVs) depend on plumpness, size, and germinability of hybrid seeds. Also, both hypotheses emphasize the importance of a balanced parental genic contribution for the normal development of endosperm. However, in the EBN hypothesis a 2 maternal∶1 paternal EBN ratio is a prerequisite for successful interspecific crossability, while the PNA hypothesis is based on the stimulative strength of the male nuclei to initiate mitotic divisions in the primary endosperm nucleus and is idependent on a 2∶1 ratio between the RV of the polar nuclei and the AV of the male gamete. Differences and similarities betweeen the EBN and PNA hypotheses are summarized and contrasted. It is proposed that EBN and PNA be considered as the same concept.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223891
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  • 10
    Electronic Resource
    Electronic Resource
    Discovery of 2n gametes in tetraploid oat Avena vaviloviana (1995)
    Springer
    Euphytica 81 (1995), S. 1-6 
    Details
    ISSN: 1573-5060
    Keywords: Avena ; 2n gametes ; binucleate cell ; evolution ; sexual polyploidization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Sexual polyploidization via the action of 2n gametes (gametes with the sporophytic chromosome number) has been identified as the most important evolutionary mode of polyploidization among plant genera. This study was conducted to determine whether 2n gametes are present in the tetraploid level of the genus Avena (2n=4×=28) Twenty tetraploid Avena lines, representing four species and one interspecific hybrid, were screened for pollen grain size in order to differentiate between n and 2n pollen. Avena vaviloviana (Malz.) Mordv. line PI 412767 was observed to contain large pollen grains at a 1.0% frequency. Cytogenetic analyses of pollen mother cells of PI 412767 revealed cells with double the normal chromosome number (i.e., 56 chromosomes at metaphase I and anaphase I). The mode of chromosome doubling was found to be failure of cell wall formation during the last mitotic division that preceded meiosis. The resulting binucleate cells underwent normal meiotic divisions and formed pollen grains with 28 chromosomes. Based on the formation and function of 2n gametes, three models involving diploid and tetraploid oat lines are proposed to describe possible evolutionary pathways for hexaploid oats. If stable synthetic hexaploid oat lines could be developed by utilizing 2n gametes from diploid and tetraploid oat species through bilateral sexual polyploidization, the resulting hexaploids could be used in breeding programs for transferring genes from diploids and tetraploids to cultivated hexaploids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00022452
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