[G02-3] Regional gravity and geoid

[G02-3-06] The gravimetric component of AUSGeoid2020 and its error model

^○Sten Claessens¹, Jack McCubbine¹, Will Featherstone¹, Nick Brown² (1.Curtin University, 2.Geoscience Australia)

As Australia is moving from the Geocentric Datum of Australia 1994 (GDA94) to the new datum GDA2020, a new accompanying quasigeoid model has been computed: AUSGeoid2020. The 2020 designation is because ITRF velocities have been used to predict the location of the datum so as to prolong its useful life. Like its predecessor AUSGeoid09, AUSGeoid2020 is built up of a gravimetric quasigeoid model that has subsequently been distorted to fit the Australian Height Datum (AHD) using cross-validated least-squares collocation. AUSGeoid2020 includes many improvements over AUSGeoid09 including use of new data and improved numerical integration routines. Another major improvement is that AUSGeoid2020 is accompanied by an error model with geographic specificity, so that users no longer need to rely on crude error estimates taken from a single nationwide comparison to GNSS-levelling data. The error estimates are propagated from uncertainties in the GNSS-levelling, terrestrial and altimeter-derived gravity anomalies and gravimetric terrain corrections. This presentation outlines the development of the gravimetric component of AUSGeoid2020 and its associated errors. Results of various numerical tests used to optimise the model are shown. Special emphasis is placed on the influence of data uncertainty on quasigeoid error estimates. The model is validated through comparison to ~7,000 GNSS-levelling data and ~1,000 historical deflections of the vertical, showing the error propagation to be realistic.