Differences between AUSGeoid09 and AUSGeoid2020

Last updated:7 June 2023

Aligned with GDA2020

The change in the reference frame used for the development of GDA2020 (i.e. ITRF2014 compared to ITRF92 used for GDA94) means the ellipsoidal height of a point in GDA94 is approximately 9 cm higher than GDA2020. As a result, AUSGeoid2020 is incompatible with GDA94. Data referenced to GDA94 is only compatible with AUSGeoid09.

Uncertainty provided

AUSGeoid09 provided an estimate of the root mean square error at the input data points used in the construction of the model. AUSGeoid2020 provides a rigorous uncertainty value associated with the offset between the ellipsoid and AHD, varying as a function of location. This value includes the uncertainty from the gravimetric component and geometric component of the model.