A COMPARISON OF GEOID UNDULATIONS FOR WEST CENTRAL GREENLAND

The accuracy of a new local gravity field model, GEOID94A, is examined at a site on the western Greenland ice sheet. The model, developed by the Danish National Survey and Cadastre, incorporates several new gra vity data sets including an extensive amount of airborne gravity data. Model-derived geoid undulations were compared to independently determ ined undulations found by differencing the elevations from Global Posi tioning System controlled airborne laser altimetry and optical levelli ng surveys. Differences between the two sets of undulations were less than +/-6 cm RMS. The comparison improved (+/-5 cm RMS) when GEOID94A undulations were adjusted by local gravity observations also acquired at the site. Our comparisons demonstrate that GEOID94A adequately mode ls the long to intermediate wavelengths of the gravity field. We concl ude that GEOID94A constitutes a reliable reference model for studies o f Greenland's gravity field.