Computation of the vertical datum relationship grids for NZVD2016

Vertical datum relationship grids allow the transformation of local vertical datum heights to NZVD2016. These transformation grids were calculated by using observation points with both an ellipsoidal and a normal-orthometric height.

The relationship between New Zealand Vertical Datum 2016 (NZVD2016) and the 13 local level datums (LVDs) has been published as a set of vertical datum relationship grids.

New Zealand Vertical Datum 2016

Local mean sea level datums

Vertical datum relationship grids

These relationship grids were calculated using geodetic control marks with both an ellipsoidal and a normal-orthometric height. The difference between to the values was modelled on a grid with a 2 arc minute spacing (approximately 3.6km). These grids only cover the areas where LINZ holds marks in a specific LVD. For example, the Auckland 1946 to NZVD2016 grid includes Auckland, Hamilton and Tauranga, but does not extend as far south as Rotorua.

Trig stations and geodetic marks

New Zealand Geodetic Datum 2000 ellipsoidal heights

Normal-orthometric height

Auckland 1946 to NZVD2016 conversion grid

The grids were computed using a ‘best fit method’, meaning that the grid is not forced to pass through the values at the observation points. Parameters allowed a point error of 1mm and a distortion error of 0.5ppm, and tend toward the mean datum relationship value (listed in the table below) in areas where there are no observation points.

Note that when using relationship grids in software such as GIS, the raster images provided in the LINZ Data Service are not a transformation surface. A surface must be created using a bi-linear interpolation method to determine the correct offset values.

Example

Vertical Datum Relationship Grid Lyttelton 1937 to NZVD2016

Map of the South Island with vertical datum overlayed

This diagram demonstrates how the difference between NZVD2016 and Lyttelton 1937 varies by 0.22 – 0.47cm across the area defined by Lyttelton datum.

The location and extent of each LVD is shown in the image below.

Map showing LVD extents over NZ

Map of New Zealand showing LVD location and extents

RegionLocal vertical datumnumber of control marksMean (m)Standard DeviationMin (m)Max (m)Range (m)Reference MarkDatum Relationship at ReferenceRelationship Grid Grid Version
One Tree Point One Tree Point 19641370.0770.042-0.030.1550.185RNZN BM (DJM9)0.080OTP64-NZVD162016.1
Auckland Auckland 19462600.2920.0290.2260.3670.14298-21 SO 69501 (DD1N)0.367AUK46-NZVD162016.1
Moturiki Moturiki 19535190.3090.0710.1400.5400.401BC 84 (B309)0.199MOT53-NZVD162016.1
Gisborne Gisborne 19262740.3430.0250.2530.3970.143GB 01 (ACVP)0.361GSB26-NZVD162016.1
NapierNapier 19622070.2030.0340.1240.2990.175H 40 (B3XM)0.193NPR62-NZVD162016.1
Taranaki Taranaki 19701250.2860.0260.2160.3560.140New Plymouth Fundamental (AGMH)0.297TNK70-NZVD162016.1
Wellington Wellington 19531370.4080.0540.2960.5170.221K 80/1 (ABPB)0.388WGN53-NZVD162016.1
Nelson Nelson 19552560.3290.0390.2150.4400.225N 1 (AC4T)0.330NSN55-NZVD162016.1
Lyttelton Lyttelton 19379230.3400.0410.2000.4890.289UD 40 (B40V)0.389LTN37-NZVD162016.1
Dunedin Dunedin 19581970.3260.0430.1740.4580.284WW 83 (AFEQ)0.377DUN58-NZVD162016.1
Dunedin-Bluff Dunedin-Bluff 19602050.2540.0390.1540.3640.210Z 41 (B3R8)0.329DBL60-NZVD162016.1
Bluff Bluff 1955710.2730.0340.2130.3520.138Bluff Fundamental (ABCC)0.316BLF55-NZVD162016.1
Stewart Island Stewart Island 197740.2990.0250.2760.3380.062N (Paterson SD) (A017)0.299STI77-NZVD162016.1
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