Realisation of a Geodetic Datum Using a Gridded Absolute Deformation Model (ADM)

This paper describes a schema for a gridded absolute deformation model (ADM) and non-linear deformation patch model that can be used to transform point positions captured in the International Terrestrial Reference Frame (ITRF), or other closely aligned reference frame, to a reference epoch consistently over time for practical applications. The schema described utilises existing models of rigid plate motion, plate boundary deformation and non-linear deformation (e.g. coseismic and postseismic effects or subsidence). Application of an ADM and patch model can enable consistent Precise Point Positioning (PPP) over time and seamless integration of Continuously Operating Reference Station (CORS) networks within deforming zones. The strategy described can also ensure consistency of time-tagged spatial datasets (e.g. laser scanned point clouds and digital cadastral databases) and GIS within a kinematic environment. An ADM can also be used as the basis for static epoch projections of a national or regional kinematic datum. A case study from New Zealand is described.