A High-Precision Deformation Model to Support Geodetic Datum Modernisation in Australia

Abstract

This paper describes a gridded kinematic representation of a deformation model that can be used to support kinematic geodetic datum applications for high precision users. The kinematic model is comprised of a site velocity model (for coordinate prediction and to model inter-seismic deformation and plate motion) and an epoch correction (patch) model. The epoch correction model estimates distortion between reference frames at the reference epoch and can include episodic deformation arising from seismic activity.

The kinematic model presented enables seamless interaction between precision GNSS positioning and related systems, GIS and static spatial datasets within a kinematic coordinate environment with centimetre precision.

The next generation Australian Geodetic Datum will be realised within a kinematic reference frame in order to capture the highest resolution deformation of the Australian tectonic plate. This represents a paradigm shift from classical geodetic datums which are realised by coordinates of geodetic monuments fixed at a specified reference epoch (static geodetic datums). Centimetre precision positioning will be available to the mass market in the near future and the disparity between static geodetic datums (and spatial data products derived from them) and ITRF due to the effects of Earth deformation will be become more apparent. As development of deformation models within GIS is still in its infancy, there is still an ongoing requirement to provide static coordinates to users to enable positioning within a kinematic reference frame to maintain alignment with existing spatial datasets (e.g., cadastral, utilities, roads, infrastructure, mining, precision agriculture, imagery and LiDar). Furthermore, a four-dimensional GIS, when developed, will still require a precise deformation or kinematic model to enable spatial data collected at different epochs to be integrated harmoniously.

The current strategy used in Australia to transform between a specified epoch of ITRF and GDA94 (the current ITRF aligned geodetic datum fixed at epoch 1994.0) is to use a 14 parameter conformal transformation but approach does not capture the full complexity and variation of the deformation field at the highest resolution for some users, and so a variable resolution gridded deformation model is proposed here as an alternative.