Heights in terms of the New Zealand Vertical Datum 2016 (NZVD2016) are similar to the historic tide-gauge based height systems in that they provide normal-orthometric heights which can be used to predict fluid flow under gravity.
However, NZVD2016 heights are referenced to a surface (NZGeoid2016), which is not directly influenced by sea-level. This means that NZVD2016 heights are able to be determined even as both the sea and land surfaces change over time.
Observing NZVD2016 Heights
Like other normal-orthometric height systems, NZVD2016 heights can be transferred to nearby marks using terrestrial levelling methods. This method is particularly practical over short distances.
NZVD2016 heights are also able to be observed using GNSS methods. An ellipsoidal height in terms of NZGD2000 can be converted to NZVD2016 by applying a correction for the Geoid model (NZGeoid2016). Many GNSS providers have incorporated this correction in their software. GNSS heights are best used for surveys where there are long distances between marks or to establish a local control point to level from.
NZVD2016 Height Control Points
NZVD2016 heights in the Geodetic Database have been determined from the National Geodetic Adjustment. These heights are nationally consistent, maintainable and have been assessed so that vertical coordinate orders are correctly assigned.
PositioNZ-Post Processing Service
The PositioNZ-PP service can be used to generate NZVD2016 heights at a location convenient to the user. It is recommended that at least 4 hours of data is collected, which will usually produce heights that are precise to 3cm at a 95 percent confidence interval.
Transforming Existing Heighted Data
LINZ provides transformations from the thirteen local vertical datums to NZVD2016. These Local Datum Relationships (or transformations) are conducted using a grid of best fit between normal-orthometric and ellipsoidal control marks within each local vertical datum.
Vertical datum transformations can be completed using the online coordinate converter tool.