Changes to the Geodetic Database
We have recently made two changes to the LINZ geodetic database – relegation of NZGD1949 information, and changing NZGD2000 coordinate orders.
NZGD1949
Ten years after the New Zealand Geodetic Datum 1949 was replaced, the NZGD1949 coordinates of marks have been removed from the mark details in the geodetic database. Until recently both the NZGD2000 coordinates and the NZGD1949 coordinates for the mark, as well as height coordinates and other mark details were shown.
We have made this change so that the default information displayed is more concise. For marks that have NZGD1949 coordinates, these are still available just on a separate page – there is a link 'NZGD1949 coordinates' on the left of the mark’s details that will take you to this information.
Associated with this change, the New Zealand Map Grid coordinates and NZMS 270 map sheet that were displayed on the mark details form have been replaced with the New Zealand Transverse Mercator coordinates and the Topo50 map sheet name. Again, for marks with NZGD1949 coordinates the old information is still available on the NZGD1949 coordinates page.
NZGD2000
The NZGD2000 coordinate orders have been changed to comply with the standards LINZS25005 (Standard for the geospatial accuracy framework) and LINZS25006 (Standard for tiers, classes, and orders of LINZ data). These standards define coordinate orders to reflect the accuracy requirements of various classes of users of the geodetic system, replacing the previous definitions that related more to the survey methodology used for measuring coordinates.
In practice this makes little difference to geodetic marks, which still have orders 0 to 6. The main change is that previously the geodetic database distinguished between order 5 marks derived from traverse data and those generated from GPS observations. The traverse based 5th order marks have been relegated to order 6, so the online geodetic database no longer distinguishes these two categories of order 5 marks.
The traverse based coordinates were relegated to 6th order as they commonly do meet the accuracy requirements for order 5 marks, and they do not have ellipsoidal height information. This change is described in detail on the LINZ website Reclassification of Order 5 (5a) Control Marks.
