Direct BEM for high-resolution global gravity field modelling |
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| Authors: | Róbert ?underlík Karol Mikula |
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| Abstract: | The paper presents a high-resolution global gravity field modelling by the boundary element method (BEM). A direct BEM formulation
for the Laplace equation is applied to get a numerical solution of the linearized fixed gravimetric boundary-value problem.
The numerical scheme uses the collocation method with linear basis functions. It involves a discretization of the complicated
Earth’s surface, which is considered as a fixed boundary. Here 3D positions of collocation points are simulated from the DNSC08
mean sea surface at oceans and from the SRTM30PLUS_V5.0 global topography model added to EGM96 on lands. High-performance
computations together with an elimination of the far zones’ interactions allow a very refined integration over the all Earth’s
surface with a resolution up to 0.1 deg. Inaccuracy of the approximate coarse solutions used for the elimination of the far
zones’ interactions leads to a long-wavelength error surface included in the obtained numerical solution. This paper introduces
an iterative procedure how to reduce such long-wavelength error surface. Surface gravity disturbances as oblique derivative
boundary conditions are generated from the EGM2008 geopotential model. Numerical experiments demonstrate how the iterative
procedure tends to the final numerical solutions that are converging to EGM2008. Finally the input surface gravity disturbances
at oceans are replaced by real data obtained from the DNSC08 altimetryderived gravity data. The ITG-GRACE03S satellite geopotential
model up to degree 180 is used to eliminate far zones’ interactions. The final high-resolution global gravity field model
with the resolution 0.1 deg is compared with EGM2008. |
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