WGS84 to NZGD2000

GPS (Global Positioning System) positions are given in terms of the WGS84 reference system.

The WGS84 reference ellipsoid is essentially the same as the Geodetic Reference System 1980 (GRS80) ellipsoid used by NZGD2000. The only variation is a small difference between the flattening terms that is insignificant at the earth's surface. This means that for most practical purposes NZGD2000 and WGS84 coordinates can be considered the same and no transformation is required.

Because NZGD2000 is fixed at 1 January 2000, WGS84 coordinates obtained at times different to this need to be "transformed" back to this epoch using the NZGD2000 deformation model. In 2008 the deformation model is applying corrections of approximately 0.5 metres. If coordinate accuracies of better than 0.5 metres are required then the deformation model will need to be applied.

This null transformation is formally defined in the LINZ standard LINZS25000 (Standard for New Zealand Geodetic Datum 2000).