MODERN HEIGHT DETERMINATION TECHNIQUES

Abstract The paper reviews a modern technique for elevation determination which avoids the costly and time-consuming spirit levelling operations. The new method is based on positioning using geodetic satellites of the NAVSTAR Global Positioning System (GPS) which can speed up the height positioning process in geodetic works. GPS provides heights above a reference ellipsoid surface and thus an extra step is required to transform these heights to meaningful orthometric or normal elevations above the geoid. This step is the computation of ellipsoid geoid/quasigeoid separations using the gravity data. The methods of gravimetric geoid determination on the territory of Poland and their accuracies are briefly outlined, as well as the accuracy of GPS-derived normal heights. The results show that there are possibilities for replacing classical levelling by the „GPS leveling” method.