NZTM2000 uses a Transverse Mercator projection and is based on the NZGD2000 datum using the GRS80 reference ellipsoid. It was chosen because it is an internationally recognised type of projection that exhibits a low level of distortion at its east-west extents. The projection is only applicable for the main New Zealand island group (North, South, Stewart/Rakiura and the smaller coastal islands). Separate projections are defined for the New Zealand's offshore islands and for its continental shelf.
NZTM2000 is formally defined in the LINZ standard LINZS25002 (Standard for New Zealand Geodetic Datum 2000 Projections). The key parameters from this standard are summarised below:
Name: New Zealand Transverse Mercator 2000
Projection type: Transverse Mercator
Reference ellipsoid: GRS80
Origin latitude: 0° 00' 00" South
Origin longitude / central meridian: 173° 00' 00" East
False Northing: 10,000,000 metres North
False Easting: 1,600,000 metres East
Central meridian scale factor: 0.9996
The predecessor projection to NZTM2000 was New Zealand Map Grid (NZMG). NZMG was based on the NZGD49 datum. More information about converting coordinates between the NZTM2000 and NZMG projections is available on the coordinate conversion pages.
"C" language source code is available to facilitate the incorporation of the NZTM2000 projection in the development of software applications.