Relative performance of AUSGeoid09 in mountainous terrain

Abstract

Abstract The Australian Height Datum (AHD) is the national vertical datum for Australia, and AUSGeoid09 is the latest quasigeoid model used to compute (normalorthometric) AHD heights from Global Navigation Satellite System (GNSS) derived ellipsoidal heights. While previous studies have evaluated the AUSGeoid09 model across Australia, such studies have generally not focused on mountainous terrain. This paper investigates the performance of AUSGeoid09 in a relative sense in the MidHunter and Snowy Mountains regions of New South Wales, from a user’s perspective. Relative (i.e. height difference between two points) comparisons were undertaken between AUSGeoid09-derived heights and officialAHDheights. The performance of AUSGeoid09 was compared to its predecessor AUSGeoid98. In both study areas, an overall improvement was evident when applying AUSGeoid09 to compute AHD height differences. AUSGeoid09 generally provided AHD height differences at the ±0.05mto ±0.09m level (1 sigma) and substantially increased the percentage of GNSS-derived height differences meeting 3rd order differential levelling specifications. This is a very encouraging result, considering the difficulties of spirit levelling in mountainous terrain and the increasing popularity of GNSS-based height transfer in practice.