New Zealand Deformation Model

New Zealand is a highly tectonically active region and it will gradually fall out of accuracy with global coordinate systems unless plate tectonics and seismic activity are accounted for. When working with coordinates with precision less than one meter, this deformation isn't an issue; otherwise, a special datum transformation type is necessary. The New Zealand Deformation Model of datum transformations adjusts for both consistent plate movement and sporadic earthquakes when converting between the NZGD2000 datum and ITRF96, using time and a system of versions issued through patches.

In most time-based transformations, time is used as an input to calculate the amount of tectonic movement between the source point and target point's measurement dates, and usually within the same Datum. For NZDM transforms, time will generally be the same between the source and target points, and is used instead to calculate the relative shifting of the Pacific and Australasian plates (surrounding New Zealand) since the last update to the model, since plates move at a consistent rate on human timescales.

Updates are occasionally released for NZDM transformations through patches, which adjust for earthquakes that have occurred since the last patch. Earthquakes deform the terrain of New Zealand in unpredictable ways, so accumulated seismic activity over every few years necessitates new survey data, which gets compiled into a new NZVD version by the government of New Zealand. The full list of versions and patches can be found on the Land Information of New Zealand's site. Versions are named according to the date that they were issued (for example, 20130801 came out on August 1, 2013), and GeoCalc uses version names as a parameter for NZDM transformations.

The "New Zealand Deformation" DatumShift has the following Parameters: