Technical Improvements on Local Geoid Model Computation

Since 2014, the National Geodetic Survey started to release experimental geoid models each year based on the new observations collected in the previous year, which are mainly from the contribution of the GRAV-D project (Gravity for the Redefinition of the Vertical Datum). While incorporating large amount of GRAV-D data into these yearly models, the implementation techniques are also polished from year to year, albeit the main architecture is still based on the Molodensky theory, essentially. This paper summarized these main technical improvements on computing local geoid models based on some hands-on experiences. It includes the update of reference models, the stabilization of airborne gravity downward continuation, the modification of residual terrain modeling, the inclusion of density variation effects, and the use of radial basis functions as well as the generalized Stokes’s integration to avoid the higher order terms. Although most of these steps are not totally independent from each other, numerical comparisons are given at each individual step to highlight their specific effects for interested researchers who may need to know the nitty-gritties. Then, the GSVS data are used to demonstrate the overall effects on the final model. Discussions for further improvements will be given at the end of the presentation.