Refining geoid and vertical gradient of gravity anomaly

:We have derived and tested several relations between geoid (N) and quasi-geoid (ζ) with model validation. The elevation correction consists of the first-term (Bouguer anomaly) and second-term (vertical gradient of gravity anomaly). The vertical gradient was obtained from direct measurement and terrain calculation. The test results demonstrated that the precision of geoid can reach centimeter-level in mountains less than 5000 meters high.