The knowledge of geopotential models accuracy and its problematic areas is necessary for all users.
In case of World Height System(WHS)development, the geopotential model accuracy limits
- WHS accuracy;
- determination of the geoidal geopotential W0;
- connection of local vertical datumto WHS;
- computation of the geopotential values W;
- height computations.
What do we need for geopotential model testing?
- Theory oftesting and its applications
- value of the geoidal geopotential W0
- four primary constants defining the level ellipsoid and its gravity field
- geopotential model evaluation and monitoring network (GMEMN), which covers (if possible) the whole Earth´s surface.
The theory for Geopotential Model Testing (GMT),developed by Burke et al. (1995), has applied to the recent EGM08 model, andfor comparison purposes, also to the previous EGM96 one. The methodology requires the four primary constantsdefining the level ellipsoid and its gravity field and accurategeocentricpositionsas well as normalMolodensky heightsof the testing sites on the Earth's surface. Over the oceans, geocentric positions, altimetricheights observed by TOPEX/POSEIDON (TP) or Jason 1 as well as hSST, obtained fromasea surface topography model (POCM4B), are also needed. No hypothetical quantities such as, for example, the orthometric heights and/or geoid heights are used in this GMT. Although a global coverage of the testing sites is preferable, regional testing networks are also useful for GMT.