Petras Petroskevicius, Rosita Birvydiene, Romuald Obuchovski

Investigation on the determination feasibility of the non-parallelity of the gravity field equipotential surfaces

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Abstract

Geodetic measurements are performed in heterogeneous gravity field. Its equipotential surfaces have a complex shape. This needs to be estimated when processing detail geodetic measurements data. Orthometric heights are calculated from one of the equipotential surface – geoid. Applying the normal height system and evaluating normal height differences needs to assess the non-parallelity of the equipotential surfaces of the gravity field. For that aim normal corrections, defining the non-parallelity of equipotential surfaces of normal gravity field and the deviation of the equipotential surfaces of real gravity field from the normal field are calculated. This work presents determination feasibility of the gravity field equipotential surfaces non-parallelity in Lithuanian territory. The six geodetic vertical network lines were selected for a research; the length of all lines is about 300 km. The gravimetric measurements by Scintrex CG-5 were performed at 203 points of the net. A mean square error of gravity acceleration values did not exceed 14 μGal. The normal corrections were calculated for measured height differences between points. A research shows that after reduction of a number of measured points twice, a mean square error of gravity acceleration values, calculated from interpolated Bouguer gravity anomalies, at the “not measured” points seeks 0.474 mGal, however the normal correction values have changed only in 0.01 mm. The use of gravity acceleration values, obtained from gravimetric map with the mean square error of 0.684 mGal, changes normal corrections up to 0.04 mm.

Keywords: Non-parallelity; equipotential surface; normal correction.