Geoid undulation differences between geopotential models

Abstract

Three geopotential models (OSU91A, GEM-T3, and GRIM4-C2), available in 1991, have been compared in several ways. The models have been differenced to find the geoid undulation difference are on the order of 1 m in land areas and 30 cm in ocean areas with extreme differences reaching 6 m. The models were also evaluated, augmented by higher degree terms, when necessary, through comparisons with undulations at Doppler and GPS positioned stations. The undulation difference at the Doppler stations was ± 1.57 m with no significant difference between models. Using 4 GPS test areas, differences were seen between the various models. A final comparison was made between geoid undulations implied by a Geosat 17 day cycle and undulations from the three models. The OSU91A model performed best having a difference standard deviation of ±34 cm.