HR: 1330h
AN: G32A-0737    [PDF]
TI: Gravity Within the Topographic Masses - Case Study Over Australia
AU: * Kuhn, M
EM: M.Kuhn@curtin.edu.au
AF: Curtin University of Technology Western Australian Centre for Geodesy, GPO Box U1987, Perth, WA 6845 Australia
AU: Claessens, S
EM: claesses@vesta.curtin.edu.au
AF: Curtin University of Technology Western Australian Centre for Geodesy, GPO Box U1987, Perth, WA 6845 Australia
AB: The behaviour of gravity within the topographic masses needs to be known for the determination of different gravity field parameters such as geoid height or orthometric height. For example, geoid determination by Stokes's formula requires downward continuation of gravity data to the geoid and the orthometric height is defined by the mean gravity along the plumb line between the Earth's surface and the geoid. In the past, different approximations (hypotheses for the topographic masses) have been used in order to derive gravity along the plumb line from the measured gravity at the Earth's surface. In this study a remove-restore technique based on the Poincar‚ and Prey reduction is used to determine gravity within the topographic masses. The actual free-air gradient in the reduced field is derived from the generalized Poisson's equation. From the gravity values given along the plumb line mean gravity as well as the mean gravity gradient are computed and compared with different (approximated) values used in the past. The results for mean gravity and the mean gravity gradient can be used in gravimetric geoid computation to realize an improved downward continuation as well as improved computation of orthometric heights from levelling and gravity measurements. Numerical results for mean gravity and the mean gravity gradient are given for two sample areas in Australia representing an area with a large range of topographic mass-density values and a mountainous area. Furthermore, the mean gravity values computed from different methods are used to estimate the effect on the orthometric height.
DE: 1212 Earth's interior--composition and state (8105)
DE: 1214 Geopotential theory and determination
DE: 1219 Local gravity anomalies and crustal structure
SC: Geodesy [G]
MN: 2003 Fall Meeting