Ocean Tide Loading Considerations for GPS Processing Around Australia

Abstract

Ocean tide loading (OTL) effects are not always modelled in static GPS data processing. In some parts of North West Australia, models suggest that (predominantly vertical) OTL induced site displacements as large as 10 cm in range can occur over the course of about 6 hours. The correct mitigation of OTL effects is consequently important if station coordinates and tropospheric delays are to be estimated from GPS data with millimetric accuracy. However, adequately modelling the site displacement due to OTL is not trivial and, in addition, displacement is not necessarily largest nearest the coast, or negligible hundreds of kilometres inland. This paper reviews how OTL site displacements are modelled, and outlines some major advances made in the modelling of the ocean tides during the last decade. Expected site displacements at a selection of sites in Australia are detailed, and the paper outlines the effects of incorrect mitigation of the OTL site displacement on GPS derived parameters, with some references to existing scientific literature.