The NSN55-NZGD2000 grid enables the conversion of normal-orthometric heights from the Nelson 1955 local vertical datum directly to New Zealand Geodetic Datum 2000 (NZGD2000) ellipsoidal heights.
NSN55-NZGD2000 is published on a one arc-minute grid (approximately 1.8 kilometres) extending over the benchmarks that nominally define the extent of the Nelson 1955 vertical datum (171.3° E to 174.4° E, 40.4° S to 42.7° S).
The conversion value is represented by the attribute “delta”, in metres.
This grid is a combination of New Zealand Quasigeoid 2016 [NZGeoid2016](https://data.linz.govt.nz/layer/3418) and the [NSN55-NZVD2016](https://data.linz.govt.nz/layer/3438) height conversion grid. Where NZGeoid2016 is the reference surface for the New Zealand Vertical Datum 2016 (NZVD2016), while the NSN55-NZVD2016 grid models the difference between the Nelson 1955 vertical datum and NZVD2016 using the LINZ GPS-levelling marks.
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).
Source
**NSN55-NZGD2000 Version 20160627**
This grid is a combination of New Zealand Quasigeoid 2016 [NZGeoid2016](https://data.linz.govt.nz/layer/3418) and the [NSN55-NZVD2016](https://data.linz.govt.nz/layer/3438) height conversion grid.
NSN55-NZGD2000 is published on a one arc-minute grid (approximately 1.8 kilometres) extending over the benchmarks that nominally define the extent of the Nelson 1955 vertical datum (171.3° E to 174.4° E, 40.4° S to 42.7° S).
The conversion value is represented by the attribute “delta”, in metres.
