Leveling, GPS and Gravity Surveys

Abstract

As the GPS survey directly determines the height of the Earth's surface from a reference ellipsoid, its combination with ordinary leveling and/or gravity measurements provides us several kinds of the gravity field quantities such as gravity anomaly, gravity disturbance and geoid height. Although these quantities have the same importance as the gravity field data, theoretically, it is meaningful to investigate the best practical ways of treating the data. We therefore present first a proper formulation by the least squares collocation as a mean to apply GPS, leveling and gravity data for a local problem, and then investigate the degree variances of the gravity field in Japan. We discuss subsequently the error estimates of the combined measurements, and finally conclude that the combined use of GPS and gravity data is quite efficient for both gravity surveys and height determinations.