EPSG:1071

The relationship between NZVD16 height and thirteen local gravity-related coordinate reference systems (LVDs) for New Zealand is available through gridded data files of offsets (sometimes called height differences). The vertical offset at a point is first interpolated within the grid of values using bi-linear interpolation. For interpolation within the offset grids, horizontal positions in the NZGD2000 geographic 2D CRS are used.

The interpolated value is then applied as an offset:
•	If the height in a LVD is required when a NZVD2016 height is given, add the interpolated offset to the NZVD2016 height (LVD height = NZVD2016 height + interpolated offset).
•	If the NZVD2016 height is required when a LVD height is given, subtract the interpolated offset from the LVD height (NZVD2016 height = LVD height - interpolated offset).

Care! In the EPSG Dataset, offsets are additive (for the forward transformation). See EPSG Guidance Note 7-2, Implementation Notes - Offsets. The LINZ convention assumes that the offset is subtracted, and grid file names reflect that convention. The offset files therefore have names which conflict with the source and target CRSs of the EPSG transformation.