The Nelson 1955 to NZVD2016 Conversion Raster provides users with a two arc-minute (approximately 3.6 kilometres) raster image of the conversion of normal-orthometric heights from the Nelson 1955 local vertical datum to the New Zealand Vertical Datum 2016 (NZVD2016).
The conversion value is represented by the attribute “O”, in metres. This conversion and NZVD2016 are formally defined in the LINZ standard [LINZS25009](http://www.linz.govt.nz/regulatory/25009).
The height conversion grid models the difference between the Nelson 1955 vertical datum and NZVD2016 using the LINZ GPS-levelling marks. From the GPS-levelling marks the expected accuracy is better than 2 centimetres (95% Confidence interval).
More information on converting heights between vertical datums can be found [on the LINZ website](http://www.linz.govt.nz/data/geodetic-services/coordinate-conversion/converting-between-nzvd2016-nzgd2000-and-local-vertical-datums).