The New Zealand Geoid 2016 (NZGeoid2016) is the reference surface for the New Zealand Vertical Datum 2016 (NZVD2016).
The geoid is an undulating equipotential surface that is related to the Earth's gravitational field that approximates level of the seas over the entire Earth. Because it is related to gravity (and therefore reflects the flow of water), it is a more intuitive reference surface than the mathematical ellipsoid.
NZGeoid2016 is published on a one arc-minute grid (approximately 1.8 kilometres) over the New Zealand continental shelf (160° E to 170° W, 25° S to 60° S). It has an expected accuracy of better than 3 centimetres based on comparisons with GPS-levelling in urban areas.
NZGeoid2016 was calculated by enhancing a global geopotential model (Eigen-6c4) using a combination of land, airborne and satellite based gravity observations together with a digital elevation model. GPS-levelling observations were not used to compute NZGeoid2016.
NZGeoid2016 can be used to transform between NZVD2016 normal-orthometric heights and NZGD2000 ellipsoidal heights, and with the published relationship grids, to the 13 local verticals datums. Note that NZGeoid2016 is not a datum in its own right, heights should not be referenced to the geoid surface directly.
Data relating to NZVD2016, including the NZGeoid2016 and the Local vertical datum relationship grids are available from the LINZ Data Service.
The authoritative .sid (Sideris grid format) files, as described in the EPSG Geodetic Parameter Registry can be download as a zip file from the Attachments section below. The data values are: nrow, ncolumn, latitude, longitude, delta-latitude (minutes), delta-longitude(minutes) and the first data value refers to the NW corner of the grid.
For software specific data formats, please contact your software vendor directly.
If you have any problems email CRM_Geodetic@linz.govt.nz.