Thursday 25 August 2005

G2
1330-1500 hours

382
A new ellipsoidal boundary value problem for geoid computation with airborne
gravimetry data in combination with all types of gravity observables
Ardalan, Alireza¹, Safari, Abdoreza¹
1 University Of Tehran, Department of Surveying and Geomatics Eng., Tehran, Iran
Author email: ardalan@ut.ac.ir
A new methodology for application of airborne gravity data in combination with various types of terrestrial gravity observation in the problem of geoid computations is developed. The developed methodology is formulated under a fixed-free two-boundary value problem. Ellipsoidal Poisson integral and its derivatives are placed at the heart of solution of the boundary value problem according to the following computational steps: (i) Reduction the effect of high frequency observations noise from airborne gravimetry data. (ii) Removal the effect of the global gravity field of the Earth in terms of high ellipsoidal harmonic expansion plus centrifugal field effect from various types of boundary data included in the problem along with the airborne gravity data. (iii) Removal the effect of residual terrain from the reduced observation of the previous step. (iv) Downward continuation of the disturbing gravity observables of various types from the surface of the Earth, for terrestrial gravity data, and from the flight level, for the airborne gravity observation to the surface of reference ellipsoid. (v) Restoration of the effect of removed global gravity field and residual terrain at the level of reference ellipsoid in terms of gravity potential. (vi) Conversion of the gravity potential values on the surface of reference ellipsoid to the geoidal undulations via ellipsoidal Bruns formula. The main high-lights of the method are: (1) Possibility of using modern high quality airborne gravimetry data, along with all existing terrestrial gravity information of any types. (2) Possibility of filling the gap between terrestrial gravity observations by airborne gravity data. (3) Keeping ellipsoidal approximation throughout the solution steps. (4) Having possibility of including the satellite altimetry data in the setup of the boundary value problem as a unified solution to geoid computation problem. Theoretical details and results of a case study will be presented.

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