Computation of the vertical datum relationship grids for NZVD2016

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.

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.

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

Region	Local vertical datum	number of control marks	Mean (m)	Standard Deviation	Min (m)	Max (m)	Range (m)	Reference Mark	Datum Relationship at Reference	Relationship Grid	Grid Version
One Tree Point	One Tree Point 1964	137	0.077	0.042	-0.03	0.155	0.185	RNZN BM (DJM9)	0.080	OTP64-NZVD16	2016.1
Auckland	Auckland 1946	260	0.292	0.029	0.226	0.367	0.142	98-21 SO 69501 (DD1N)	0.367	AUK46-NZVD16	2016.1
Moturiki	Moturiki 1953	519	0.309	0.071	0.140	0.540	0.401	BC 84 (B309)	0.199	MOT53-NZVD16	2016.1
Gisborne	Gisborne 1926	274	0.343	0.025	0.253	0.397	0.143	GB 01 (ACVP)	0.361	GSB26-NZVD16	2016.1
Napier	Napier 1962	207	0.203	0.034	0.124	0.299	0.175	H 40 (B3XM)	0.193	NPR62-NZVD16	2016.1
Taranaki	Taranaki 1970	125	0.286	0.026	0.216	0.356	0.140	New Plymouth Fundamental (AGMH)	0.297	TNK70-NZVD16	2016.1
Wellington	Wellington 1953	137	0.408	0.054	0.296	0.517	0.221	K 80/1 (ABPB)	0.388	WGN53-NZVD16	2016.1
Nelson	Nelson 1955	256	0.329	0.039	0.215	0.440	0.225	N 1 (AC4T)	0.330	NSN55-NZVD16	2016.1
Lyttelton	Lyttelton 1937	923	0.340	0.041	0.200	0.489	0.289	UD 40 (B40V)	0.389	LTN37-NZVD16	2016.1
Dunedin	Dunedin 1958	197	0.326	0.043	0.174	0.458	0.284	WW 83 (AFEQ)	0.377	DUN58-NZVD16	2016.1
Dunedin-Bluff	Dunedin-Bluff 1960	205	0.254	0.039	0.154	0.364	0.210	Z 41 (B3R8)	0.329	DBL60-NZVD16	2016.1
Bluff	Bluff 1955	71	0.273	0.034	0.213	0.352	0.138	Bluff Fundamental (ABCC)	0.316	BLF55-NZVD16	2016.1
Stewart Island	Stewart Island 1977	4	0.299	0.025	0.276	0.338	0.062	N (Paterson SD) (A017)	0.299	STI77-NZVD16	2016.1