FIND OUT MORE... GPS in New Zealand
The Global Positioning System (GPS) is one of a number of satellite-based Global Navigation Satellite Systems (GNSS). GPS was first developed by the United States military, but today it is operated by military and civilian agencies and is used for many civilian applications worldwide, including navigation and accurate surveying.
LINZ provides information and services to support GPS use, but GPS is not governed or regulated by New Zealand agencies. Many survey firms and other commercial companies also provide GPS positioning services.
New Zealand equivalence
GPS coordinates are equivalent to those in terms of the New Zealand Geodetic Datum 2000 (NZGD2000) and projection coordinates in terms of New Zealand Transverse Mercator 2000 (NZTM2000). GPS coordinates can easily be converted into New Zealand Transverse Mercator 2000 (NZTM2000) projection coordinates that will be used for the future Topo50 1:50,000 map series and other small-scale mapping.
If you're using GPS, its coordinates may not correspond with current New Zealand topographic maps that are in terms of New Zealand Map Grid (NZMG). However, GPS coordinates can be uploaded to LINZ's website, where coordinate conversions can be used to determine a position in terms of these maps.
Improving accuracy
A single GPS receiver will provide coordinates that are accurate to approximately 10 metres, but various techniques are available to improve the positioning accuracy.
In New Zealand, LINZ operates a nationwide network of 30 continuously tracking GNSS stations called PositioNZ. It provides GPS observations which can be used with GPS station data to improve position accuracy. Observation data from the 30 stations can be downloaded free of charge - see PositioNZ network.
How GPS works
GPS is a constellation of 24 satellites orbiting twice every 24 hours at approximately 20,000 kilometres above the Earth. The satellites transmit a number of radio signals that enable receivers on the ground to determine their position. By using three satellites, the longitude and latitude of the receiver can be determined, and if four satellites are used, the height of the receiver is also determined.
The accuracy of positions using GPS varies from approximately 10 metres to a few millimetres, depending on the type of receiver and the method used.
Find out more about how GPS systems work at:
