Recovering Orthometric Height Differences from GPS Data and Geopotential Models

Gomaa Dawod and Mona El-Kady

Abstract:	Determining orthometric heights is required for most engineering projects. In order to convert the ellipsoidal heights obtained from GPS observations to orthometric heights, some knowledge of the geoidal undulations is needed. The use of the spherical harmonic geopotential models can be a time saving and cost-effective tool to perform this task. Using the OSU9 1 A geopoten tial model, a strategy is presented to transform the GPS-derived geodetic height differences to orthometric height differences. The method is used to perform a regression analysis to fit the computed undulation differences (of points having both geodetic and orthometric heights) over the area of interest, in order to obtain a mathematical model that is a function of geographic coordinates. The predicted undulation differ- ences are then added to the GPS height differences to compute orthometric height differences. A data set in Egypt is used to test the proposed technique. The obtained results show an average error value of 8 cm for orthomeuic height differences. This error magnitude may be suitable for densitication purposes, particularly for resource management in such areas where sufficient precise leveling is unavailable.
Published in:	Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993) September 22 - 24, 1993 Salt Palace Convention Center Salt Lake City, UT
Pages:	1089 - 1089
Cite this article:	Dawod, Gomaa, El-Kady, Mona, "Recovering Orthometric Height Differences from GPS Data and Geopotential Models," Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993), Salt Lake City, UT, September 1993, pp. 1089-1089.
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