How is the geoid model validated?
A geoid model can be validated in two ways: error propagation and independent datasets. For the former, the challenge is to associate a realistic error model to the input data required in the determination of a geoid model. This internal accuracy can be too optimistic because it will not consider systematic errors and omissions. For the latter, GPS on BMs is the most common approach. It consists of comparing the geoid models (N) to geoid heights determine from GPS ellipsoidal heights (h) and spirit leveled orthometric height (H): h – H – N = ε. The discrepancies ε should be zero (or a constant) if each height would be errorless. The problem with this technique is the difficulty to disassociate errors from the geoid model, levelling data, GPS measurements and stability of the BMs. Other independent techniques for validation could be satellite radar altimetry and astro-geodetic deflections of the vertical.
