GPS Coordinate Transformations and their Use in Gravimetry

Abstract

Geodetic coordinates on Australian maps are referenced to the Australian Geodectic Datum 1984 (AGD84). Topographic elevations are referred to the Australian Height Datum (AHD). Conversely, GPS yields 3-D Cartesian coordinates and coordinate differences in the World Geodetic System 1984 (WGS84).The difference between coordinates of the same point on the Earth's surface varies between 150 m to 200 m over continental Australia. This study presents a method of transforming between GPS (WGS84) and AGD84 latitude, longitude and AHD. This permits GPS-aided gravity data to be integrated with other geophysical data referred to the AGD84. A new rigorous formula to simultaneously determine the latitude, free-air and slab Bouguer corrections from GPS and geoid information is derived. It is demonstrated that, if an incorrect elevation datum is used for gravimetric data reduction, a different gravity anomaly is produced.