Orthometric Heights Without Leveling

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Abstract
Orthometric heights can be obtained without leveling by combining gravimetrically determined geoidal heights and ellipsoidal heights derived from Global Positioning System (GPS) interferometry. The accuracy of the orthometric heights is dependent on the accuracy of each of the two components. The paper discusses and compares different methods of geoid determination and evaluates their accuracy. The analysis shows that in areas well‐covered by gravity data, the determination of geoidal height differences is currently at least as accurate as the determination of ellipsoidal height differences by GPS‐phase measurements. Thus, orthometric height differences in these areas can be obtained by this method with an accuracy of 2 to 3 ppm. This opens interesting possibilities for orthometric height determination in the mountains and in remote areas without vertical control. Results from two test areas confirm this analysis. A brief discussion of the requirements for an accuracy of 0.3 ppm concludes the paper.