Advances in the numerical solution of the linear molodensky problem     

M. G. Sideris  K. P. Schwarz 《Journal of Geodesy》1988,62(1):59-70

The solution of the linear Molodensky problem by analytical continuation to point level is numerically the most convenient of all the theoretically equivalent solutions. It is obtained by successively applying the same integral operator and it does not depend explicitly on the terrain inclination. However, its dependence on the computation point restricts somehow the computational efficiency. The use of the Fourier transform for the evaluation of the integral operator in planar approximation lessens significantly the burden of computations. Using this spectral approach, the problem has been reformulated and solved in the frequency domain. Moreover, it is shown that the solution can be easily split into two steps: (a) “downward” continuation to sea level, which is independent of the computation point, and (b) “upward” continuation from sea to point level, using the values computed at sea level. Such a treatment not only simplifies the formulas and increases the numerical efficiency but also clarifies the physical interpretation and the theoretical equivalence of the continuation solution with respect to the other solution types. Numerical tests have been performed to investigate which terms in the Molodensky series are of significance for geoid and deflection computations. The practical difficulty of differences in the grid spacings of gravity and height data has been overcome by frequency domain interpolation. Presented at theXIX IUGG General Assembly, Vancouver, B.C., August 9–22, 1987.  相似文献   

A unified approach to post-mission processing of intertial data     

K. P. Schwarz 《Journal of Geodesy》1985,59(1):33-54

The outpout of inertial survey systems is available to the user in two basic forms: as Kalman filtered information at updates or as integrated velocity and position information at regular time intervals. In case of the second data type, the post-mission processing starts with the approximation of the velocity error curve. This approximation is either based on a system error model as in Kalman filtering or uses curve fitting techniques. From there on, smoothing or adjustment procedures are used as further steps in the post-mission treatment of both data types. A unified treatment of the various post-mission approaches starts with the formulation of appropriate error models of the system outputs. It is then possible to present all existing methods as intermediate steps of a rigorous adjustment procedure. This unified approach gives insight into the limitations of individual methods and provides a means to detect inconsistencies in post-mission processing strategies. An analysis of existing approaches is made and a new method, spectral decomposition, is treated in detail. Compared to the existing procedures, it has advantages with respect to a rigorous covariance propagation and blunder detection.  相似文献   

Report on the International Summer School on Local Gravity Field Approximation     

J. Y. Chen  K. P. Schwarz 《Journal of Geodesy》1985,59(1):107-108

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The geodetic requirements for commercial data base management systems     

Charles R. Schwarz 《Journal of Geodesy》1982,56(2):165-176

There are many data base management systems now available as commercially marketed software packages. Although most of these packages were initially aimed at bussiness or administrative data processing applications, they may frequently also be the right tool for a scientific data processing task. This becomes more apparent as we notice that scientific computer programmers are spending more and more time on data management requirements rather than the coding of mathematical algorithms. In a scientific environment, a generalized data base management package is best viewed as a tool for programmers, rather than as a tool for direct, independent use by end users or by agency management. To the end user, the most attractive feature of a commerical DBMS is usually the interactive retrieval and update language. To the programmer, the most attractive feature is more likely to be the strong support for various types of keyed access. All of the manipulations necessary to build and maintain indices and other tables can be treated as procedural abstractions. Coupled with a procedural language, a DBMS offers the programmer a higher level (in the sense of more abstract) language. The most important geodetic requirement on a commercial DBMS is therefore that the package contain a strong Data Manipulation Language, with strong support for the algorithmic language used for scientific processing. Presented at International Symposium on Management of Geodetic Data, Copenhagen, August 24–26, 1981.  相似文献   

Deriving Acceleration from DGPS: Toward Higher Resolution Applications of Airborne Gravimetry     

A. M. Bruton  K. P. Schwarz  S. Ferguson  M. Kern  Ming Wei 《GPS Solutions》2002,5(3):1-14

Although airborne gravimetry is now considered a fully operational technique, errors due to motion compensation using differential GPS (DGPS) continue to influence both its accuracy and the range of applications in which it can be used. In typical medium-resolution applications such as airborne geoid mapping, errors due to DGPS contribute considerably to the error budget of an airborne gravity system. At the same time, efforts to increase the resolution of such systems for demanding applications such as resource exploration remain impedded by errors in DGPS. This article has three objectives. The first one is to compare eight industrially relevant DGPS software packages for the determination of aircraft acceleration. The second objective is to analyze and quantify the effect that each relevant portion of the DGPS error budget has on the determination of acceleration. Using data sets that represent a wide range of operational conditions, this is done in the frequency domain over a range of frequencies corresponding to spatial resolution as high as 450 m. The third objective is to use that information to recommend and demonstrate approaches that optimize the estimation of aircraft acceleration for determining the geoid and for resource exploration. It is shown, for example, that the time of day in which the survey is carried out and the dynamic characteristics of the aircraft being used are two of the most crucial parameters for very high-resolution gravity field estimation. It is demonstrated that when following the above-mentioned recommendations, agreements with ground daa of better than 1.5 and 2.5 mGal can be achieved for spatial resolutions (half-wavelengths) of 2.0 and 1.4 km, respectively. ? 2002 Wiley Periodicals, Inc.  相似文献   

Electronic structure and electric field gradient calculations of Al2SiO5 polymorphs     

M. Iglesias  K. Schwarz  P. Blaha  D. Baldomir 《Physics and Chemistry of Minerals》2001,28(1):67-75

 The electronic structure of the three polymorphs of Al₂SiO₅, andalusite, sillimanite, and kyanite, is studied by linearized-augmented-plane-wave (LAPW) calculations using the WIEN code. Total energy calculations verify, in agreement with recent pseudopotential calculations, that andalusite is the most stable phase, followed by sillimanite and kyanite.We determine the electronic charge density distribution and find strong polarizations on all oxygen ions. We identify different polarizations due to Al or Si neighbors which depend on their respective distances to the oxygen atom. The chemical bonding is not purely ionic in nature but has important covalent contributions. Electric field gradients (EFGs) at all sites are calculated and agree well (within 10%) with available experimental data on Al. We identify the origin of the EFGs and demonstrate its relation to the nearest-neighbor coordination and the resulting anisotropy of the electronic charge distribution. Received: 22 March 2000 / Accepted: 3 August 2000  相似文献   

Analysis of geodetic satellite (Geos I) observations in North America     

I. I. Mueller  C. R. Schwarz  J. P. Reilly 《Journal of Geodesy》1970,44(2):143-162

Geos I observations made at thirty optical and four Secor stations were analyzed in the geometric and short-arc modes for the purpose of detecting systematic distortions in the North American Datum. The results indicate that the Nad at its origin (Meades Ranch, Kansas) requires an easterly rotation in azimuth and a westerly rotation in the prime vertical plane, both in the magnitude of one second of arc to fit the satellite data. There is also evidence of the need for a reduction in scale of about 1:200.000.  相似文献   

A study on the combination of satellite, airborne, and terrestrial gravity data   总被引：3，自引：2，他引：1  

M. Kern  K. K. P. P. Schwarz  N. Sneeuw 《Journal of Geodesy》2003,77(3-4):217-225

Satellite gravity missions, such as CHAMP, GRACE and GOCE, and airborne gravity campaigns in areas without ground gravity will enhance the present knowledge of the Earths gravity field. Combining the new gravity information with the existing marine and ground gravity anomalies is a major task for which the mathematical tools have to be developed. In one way or another they will be based on the spectral information available for gravity data and noise. The integration of the additional gravity information from satellite and airborne campaigns with existing data has not been studied in sufficient detail and a number of open questions remain. A strategy for the combination of satellite, airborne and ground measurements is presented. It is based on ideas independently introduced by Sjöberg and Wenzel in the early 1980s and has been modified by using a quasi-deterministic approach for the determination of the weighting functions. In addition, the original approach of Sjöberg and Wenzel is extended to more than two measurement types, combining the Meissl scheme with the least-squares spectral combination. Satellite (or geopotential) harmonics, ground gravity anomalies and airborne gravity disturbances are used as measurement types, but other combinations are possible. Different error characteristics and measurement-type combinations and their impact on the final solution are studied. Using simulated data, the results show a geoid accuracy in the centimeter range for a local test area.  相似文献   

Biomasseuntersuchungen am Zooplankton der ostmecklenburgischen Küstengewässer - ein Beitrag zum Eutrophiestatus. Teil 4: Zur Biomasse und Topographie der Boddenketten von Rügen     

S. Schwarz 《洁净——土壤、空气、水》1978,6(4):299-306

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Biomasseuntersuchungen am Zooplankton ostmecklenburgischer Küstengewässer - ein Beitrag zum Eutrophiestatus. Teil 8: Zur Biomasse des Peenestromes bei Wolgast     

S. Schwarz 《洁净——土壤、空气、水》1979,7(1):133-135

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