From 1st July 2017, both Nelson City and Tasman District Councils became the first Territorial Authorities to use New Zealand Vertical Datum 2016. Now more than half of NZ territorial authorities plan to be using NZVD2016 by 2022.
This photo of Champion Road (at C7T2 – SS 95) demonstrates that the height difference between the two regions is mathematical only.
NZVD2016 is New Zealand’s official height system. It allows for the consistent collection and seamless exchange of heights across New Zealand. This means that heights used in GIS, infrastructure, planning, consents and works can now be nationally standardised.
Traditionally a height from tide gauge has been used as a reference point. However, these heights can be misleading as local sea level varies around the coastline and the reference points are historic.
As such each local authority has determined their own height level reference. In some cases, multiple height systems are used within a district. In the case of upper-South Island:
The shared boundary between Nelson City and Tasman District council’s, Champion Road, became a “Canyon” in the regional GIS viewer Top of the South Maps. Jumping from 9 metres on the Tasman side to 22 metres on the Nelson side - a difference of 12.07 metres.
Changing the vertical datum of a data set is relatively straight forward, with a number of tools available to make the changes i.e.
This way all uses can quickly see that data collected after uptake date is in terms NZVD2016 and any data prior to this date can be treated with historic assumptions and individually investigated.