PAGravf4.5 program demo for Precise approach and all-element modelling on Earth gravity fieldIssuing time:2024-11-09 16:33Link:http://www.zcyphygeodesy.com/en/ ![]() Precise Approach of Earth Gravity Field and Geoid PAGravf4.5 includes the basic principles, main methods and all the formulas in physical geodesy and Earth gravity field have been realized completely to imporve high education environment. Many long-term puzzles such as various terrain effects on various observations, all-element analytical modelling on gravity field, fine gravity prospecting modelling from heterogeneous observations, external accuracy index measurement and computational performance control have been effectively solved to strengthen the application capacity of Earth gravity field. PAGravf4.5 sets up the scientific gravity field approach system with the spatial domain integration algorithms based on boundary value theory and spectral domain radial basis function approach algorithms to realize the all-element analytical modelling on gravity field in whole space on or outside the geoid from various heterogeneous observations in the different altitudes, cross-distribution and land-sea coexisting cases. ☆ Technical features of gravity field Integral algorithm (1) The fixed integral radius for local gravity field refinement Limiting the definition domain of kernel function, PAGravf4.5 executes the gravity field integral operation with the given radius, including numerical integral and FFT integral algorithm (kernel function windowing), to coordinate and unify various gravity field approach algorithms. Two-dimensional FFT adopts the modified two-dimensional planar kernel function, whose calculation accuracy is not significantly different from that of one-dimensional FFT in the range of latitude 10°. (2) The calculation point and the move point (integral running areal element) The coordinates of geodetic points are expressed as the latitude, longitude and ellipsoidal height. For example, the location of boundary surface, measurement point, calculation point and integral move point (areal element or volume element) are expressed by geodetic coordinates. The integral cell-grid location is the geodetic coordinates of the center of the cell-grid, and the integral radius is calculated by geodetic coordinates. (3) The equipotential boundary surface Most gravity field integral formulas are derived from Stokes boundary value theory, such as the Hotine integral, Vening Meinesz integral, radial gradient integral formula, etc. The solution of Stokes boundary value problem requires that the boundary surface is an equipotential surface, that is, the anomalous gravity field elements should be located on some an equipotential surface. In PAGravf4.5, it can meet most requirements that the accuracy of the ellipsoidal height employed as the boundary surface is not less than 10 m. The boundary surface can be constructed from a 360-degree global geopotential coefficient model, which can also be replaced by the ellipsoidal height grid of normal or orthometric equiheight surface in near-surface space. ☆ The typical technical features of SRBF approach program in PAGrav4.5 (1) The analytical function relationships between gravity field elements are strict, and the SRBF approach performance has nothing to do with the observation errors. (2) Various heterogeneous observations in the different altitudes, cross-distribution, and land-sea coexisting cases can be directly employed to model the all-element gravity field models on or outisde the geoid without reduction, continuation and griding. (3) Can integrate very few astronomical vertical deflection or GNSS-levelling data, and effectively absorb the edge effect. (4) Has the strong capacity in the detection of observation gross errors, measurement of external accuracy indexes and control of computational performance. The typical complex gravity field feature area selected where residual gravity disturbance variation exceeds 300mGal after the 540-degree reference model value removed, you can verify and analyze the performance of various gravity field approach algorithms in this group of programs to facilitate and quickly grasp the characteristics and usage of these algorithms.
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