New Zealand Map Grid (NZMG)

New Zealand Map Grid (NZMG) was previously used as the projection for topographic 1:50,000 and other small-scale mapping in mainland New Zealand. New Zealand Transverse Mercator 2000 (NZTM2000) replaced NZMG in 2001 and is now the official projection used in New Zealand.

Read about New Zealand Transverse Mercator 2000 (NZTM2000)

New Zealand Map Grid (NZMG) was used to produce New Zealand Map Series 260 (NZMS260), the 1:50,000 topographic maps used in New Zealand (except for the Chatham Islands) until 2021. It was based on the NZGD1949 datum:

New Zealand Geodetic Datum 1949

NZMG was not a geometric projection, so it is not based on a shape. Instead, it used a mathematical expression which combined complex numbers and polynomial terms. This meant that the formula could be tailored to minimalize distortion over New Zealand, but it was unique to New Zealand and could be difficult to include in computer software and navigation equipment.

NZMG was replaced by New Zealand Transverse Mercator 2000 (NZTM2000) in 2001. NZTM2000 is the official projection used in New Zealand, based on New Zealand Geodetic Datum 2000 (NZGD2000).

The transformation of coordinates between NZMG and NZGD2000 is not straightforward, and it is not possible to have NZMG coordinates in terms of NZGD2000 and vice versa. More information about converting coordinates between projections is available on the coordinate conversion pages:

Understanding coordinate conversions

NZMG was described in:

A Conformal Mapping Projection with Minimum Scale Error - W. I. Reilly (1973)

The key parameters are summarised below
NameNew Zealand Map Grid
EPSG number27200
Projection typeConformal (orthomorphic)
Reference ellipsoidInternational 1924
DatumNew Zealand Geodetic Datum 1949 (NZGD1949)
Origin latitude41° 00' 00" South
Origin longitude173° 00' 00" East
False Northing6,023,150 metres North
False Easting2,510,000 metres East

For information on including the NZMG projection in the development of software applications, as well as source code and data, see:

Geodetic software downloads

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