Abstract:
In GNSS, 3D geometric position is calculated with high accuracy. This position is the ellipsoidal latitude, longitude and ellipsoidal height (λ,ϕ,h)(λ,ϕ,h) with respect to WGS84 coordinates system. These coordinates are integrated with local horizontal/projected coordinates (X, Y) by mathematical coordinate’s transformations and map projections. The geometric ellipsoidal height (h) obtained by means of GNSS has to be integrated with the physical/orthometric heights (H) obtained by means of precise leveling. The physical surface defining the difference between both height systems is the geoid represented by the geoid undulation (N) at a given position. Different methods are used to build geoid models. Global models using terrestrial and satellite data are available to calculate the geoid heights as function of the earth potential (W). The most recent high degree and order models are EGM2008, Eigen05c, Eigen06c4, etc. (GFZ-Potsdam, ‘List of available global models. http://icgem.gfz-potsdam.de/ICGEM/modelstab.html, 2017). Some regional geoid models are available like the European Gravimetric Geoid (EGG97). These models mostly do not fit the local datum due to datum definition problems. Here, a group of precise height reference benchmarks measured with GNSS is used to fit the global models with the local vertical datum to define the local height reference system of Palestine. The accuracy of the different global geopotential models is evaluated before and after the application of the geoid fitting.
