Detection of Local Geoid Deformations by Gravity Disturbances from GPS/Gravimetric Observations

Abstract

This paper deals with a method for detection of local geoid deformations; as a consequence, the method’s main application concerns geoid adjustment to GPS/levelling points. This is based on the fact that these points should present no local geoid deformation to avoid errors in the adjustments. These type of miscalculations would lead to an incorrect adjustment and result in further errors in subsequent studies with GPS in the proximity at the point with local deformation.

The method proposed is based on predictions of gravity disturbance from geoid undulations using Poisson integral with modified kernel, and its comparison with the gravity disturbance from GPS and gravimetric observations.

The use of gravity disturbance instead of gravity anomalies has been chosen since gravity disturbance is a quantity derived from GPS and not from levelling. The loss of accuracy arising with a local height reference system is therefore theoretically avoided as far as the differences in geodetic reference systems regarding positions of gravity measurements and coefficients of the global models are accounted for.

Extended numerical tests using computed geoidal undulations and the corresponding gravity disturbances obtained from the geopotential model GPM98cr computed up to degree 720 illustrate the validity of the proposed method and its usefulness as local geoid deformations detection tool.

Finally, the method is tested using real GPS/Gravimetric data and geoid models IBERGEO95 and EGG97 with good results.