Refinement of Gravimetric Geoid Using GPS and Levelling Data

Abstract

A gravimetric geoid model does not allow the accurate transformation of Global Positioning System (GPS) ellipsoidal heights to Australian Height Datum (AHD) heights in the Perth region of Western Australia. This is predominantly due to the effect of the geological structures associated with the Darling Fault, the availability and quality of data, and the possibility of distortions in the AHD. Therefore, a combined solution is sought, where 99 co-located GPS and AHD heights are used to adjust the gravimetric geoid such that it provides a model of the separation between the AHD and the GRS80 reference ellipsoid. This data combination was investigated using least squares collocation and continuous curvature splines in tension. The least squares collocation technique was found to give an improved model of the AHD-GRS80 separation, as shown by a standard deviation of fit of the combined model to the control data of ±8 mm. In comparison, the gravimetric geoid gives a standard deviation of fit to the control data of ±128 mm.