1993 Vol. 18, No. 3
This paper presents a new method for the computation of the Stokes formula using the Fast Hartley Transform(FHT) techniques. The algorithm is most suitable for the computation of real sequence transform, but the Fast Fourier Transform (FFT) techniques is more suitable for the computation of complex sequece transform. The solution of Stokes formula is, however, only associated with a real sequence problem. Therefore the computation of the Stokes formula using FHT techniques is more efficient than using FFT techniques. The procedures of the evaluation of the Stokes formula by FHT techniques are described in detail and correspondingly, some numerical tests are given. By the comparison with both FFT techniques and numerical integration method, the results show that the resulting values of geoidal undulations by FHT techniques are almost the same as by FFT techniques, and the computational speed of FHT technique is about two times faster than that FFT techniques.
Because of the rugged topography in the west Sichuan province, it is very difficult to carry out the conventional surveying there. If the GPS technique is used to provide the control of photography. the geodetic field work will be much easier and more economical. But the GPS given ellipsoidal heights must be converted to normal heights. So a quasi-geoid with high resolution is needed in this area. In this paper, a 5'×5' gridded quasi-geoid has been computed over a 14°×12årea in west Sichuan by using FFT method which employed the planar-approximated Stokes integral. The Molodensky first-oder approximate term has been also considered in the computation. Comparing the results with some astrogravimetric levelling and GPS levelling, We found that they are about 1 meter in accuracy. Furthermore, the study shows that the results including the contribution of residual gravity anomalies are 20 percent more accurate than geopotantial model only derived quasi-geoid and another 20 percent improvement can be obtained by considering the Molodensky first-oder approximate term using a 0.5'×0.5' DTM.
A variational principle is presented in this paper for directly calculating the potential coefficients in solving the mixed boundary value problem. According to the principle, potential coefficients can be obtained directly in solving the mixed boundary value problems of first, second and third type. The principle can be used for studying Earth' s gravity field jointly applying the classical gravimetric(the gravimetric points are positioned using classical geodetic method such as trianglation and geometric levelling), satellite gravimetric (the gravimetric points are positioned by satellite positioning techniques) and satellite altimetric data.
Height anomaly, deflection of the vertical and disturbing gravity are a set of parameter used most often in geodesy and space research. After analyzing the source of the error caused in computing the parameters above, this paper demonstrates in detail the special requirements of the integration element on computing. Then the Gauss integration is used to compute gravimetric quantities. The computational results show that the new method not only provide an accuracy value and save the computational time, but also come over the singular integrations in numerical computation of the earth' gravity field in one way.
In this paper, the authors discussed the inertial properties of the geocentral stellar reference system (GSS) and the geocentral innate reference system (GIS), and pointed out that, in the region where, for an arbitrary point P, the distance from P to the Earth's centeris larger than 160 km ,GSS is better than GIS. However, to study some effects in the system of artificial satellite, it is better to choose a satellite stellar reference system whose center is located at the mass center of the artificial satellite.
This paper briefly discusses the investigating results of the motivation on the uplifting and thickening of the crust in the area of Qinghai-Xizang plateau achieved up to now by geologists and geophysicists, and presents some proposals and viewpoints related with the geodetic research on this problem.
Starting from the equations of Solid Mechanics, one type of inverse problem in the form of the defferential equation is proposed and defined as the inverse problem of Dynamic Geodesy. The properties and solutions of the inverse problem are investigated by the finite element method and regularization method, and a regularization method for inversion of dynamic geodetic data is given. Finally, the application of the inversion method in the research of the non-uniform rupture of earthquakes is discussed, and the pattern of the coseismic non-uniform rupture of the Tangshan earthquake of 1976 is determined by inversion of geodetic data.
This paper studies the eatimation of variance and covariance components for GPS baseline network by MINQUE method. The fundamental rule to select variance—covariance model has been presented, and the alternative algorithm which simulaneously estimate fixed variance components and scalled variance components of the distance, azimuth and geodetic height difference for a GPS baseline vector has been developed.
By GPS positioning, we can obtain the three-dimensional coordinates of stations: latitude B, longitude L and ellipsoidal height H. One of the reason is lower of altimetric accuracy. In order to exploit the potentialities of the accuracy of the heisht provided by GPS position and to make full use of the valuable resources, we analyse the factors affecting the accuracy of the height, propose, the ways and measures to eliminate or reduce the aforementioned errors. Finally an example is given to indicate that the GPS Positioning may be used instead of the first order and second order levelling in determination of crust deformation and other applications.
GPSGSM is the core of Management System of Geology and Surveying in Underground Mine, with the goal of automatic processing of graphic data, computer aided mapping and its dynamic modification. It will be realized by this system that automatic deducing the boundary line of ore bed by means of AI technique, producing and modifying maps of Geologyand Surveying in Mine, providing all technical information for daily management of Geology and surveying and calculating ore reserves.This paper introduces its general design, structure and functions, technique of realization and application, etc.
Inthis paper, the principles of the methods of inverting modulus with displacement data which were observed in concrete dams are discussed. Then, the author pointed out the key problems in calculation and the methods of resolving the problems. In the end, the author gives two examples for how to inverte the modulus.
In order to improve the reliability of population data analysis and the prediction of population models, this paper presents various methods for enhancing the quality of simulation of the population functions based on cleaning statistic data and selecting suitable, mathematical functions. The introduction of robust estimators to data processing and simulation could strengthen the resistance of the population models against outliers or gross errors. The accuracy of the simulation could be improved by choosing proper mathematical functions. The research in this article shows that the accuracy and reliability of population models derived from the suggested methods are better than classical approaches.