Understanding coordinate conversions

A geographic coordinate (latitude, longitude and ellipsoidal height) is in terms of a geodetic datum (eg NZGD2000, NZGD1949). The two main ways to transform geographic coordinates between geodetic datums - use a transformation grid or a similarity transformation - are shown in the diagram below.

This page holds information regarding conversion between NZVD2016, NZGD2000 and local vertical datums.

A projection coordinate (northing and easting) is in terms of a specific projection (e.g. NZTM2000). Every projection is defined in terms of a geodetic datum. When comparing coordinates it is critical that they are in terms of the same projection or else errors will be introduced.

How to transform heights between vertical datums.

The following table provides examples of the transformation of heights between different datums and systems.