Coordinate Operations¶

Reprojection Console¶

The reprojection console (in Demos => Reprojection console) lets quickly test coordinate operations. Use it to convert a single coordinate or WKT geometry, and to see the operation details GeoServer is using. It is also useful to learn by example when you have to Define a custom Coordinate Operation.

Reprojection console showing operation details and a transformed coordinate pair.

Add Grid Shift Transform files¶

GeoServer supports NTv2 and NADCON grid shift transforms. Grid files are not shipped out with GeoServer. They need to be downloaded, usually from yor National Mapping Agency website.

1. Search for the Grid File Name(s) int the tables below, which are extracted from EPSG version 7.9.0. If you need to use a Grid Shift transform not declared in EPSG, you will need to Define a custom Coordinate Operation.
2. Get the Grid File(s) from your National Mapping Agency (NTv2) or the US National Geodetic Survey (NADCON).
3. Copy the Grid File(s) in the user_projections directory inside your data directory.
4. Use the Reprojection Console to test the new transform.

Define a custom Coordinate Operation¶

Custom Coordinate Operations are defined in epsg_operations.properties file. This file has to be placed into the user_projections directory, inside your data directory (create it if it doesn’t exist).

Each line in epsg_operations.properties will describe a coordinate operation consisting of a source CRS, a target CRS, and a math transform with its parameter values. Use the following syntax:

<source crs code>,<target crs code>=<WKT math transform>

Math transform is described in Well-Known Text syntax. Parameter names and value ranges are described in the EPSG Geodetic Parameter Registry.

4230,4258=PARAM_MT["NTv2", \
  PARAMETER["Latitude and longitude difference file", "100800401.gsb"]]

4230,4258=CONCAT_MT[PARAM_MT["Ellipsoid_To_Geocentric", \
  PARAMETER["dim", 2], \
  PARAMETER["semi_major", 6378388.0], \
  PARAMETER["semi_minor", 6356911.9461279465]], \
PARAM_MT["Position Vector transformation (geog2D domain)", \
  PARAMETER["dx", -116.641], \
  PARAMETER["dy", -56.931], \
  PARAMETER["dz", -110.559], \
  PARAMETER["ex", 0.8925078166311858], \
  PARAMETER["ey", 0.9207660950870382], \
  PARAMETER["ez", -0.9166407989620964], \
  PARAMETER["ppm", -3.5200000000346066]], \
PARAM_MT["Geocentric_To_Ellipsoid", \
  PARAMETER["dim", 2], \
  PARAMETER["semi_major", 6378137.0], \
  PARAMETER["semi_minor", 6356752.314140356]]]

23031,25831=PARAM_MT["Affine", \
  PARAMETER["num_row", 3], \
  PARAMETER["num_col", 3], \
  PARAMETER["elt_0_0", 1.0000015503712145], \
  PARAMETER["elt_0_1", 0.00000758753979846734], \
  PARAMETER["elt_0_2", -129.549], \
  PARAMETER["elt_1_0", -0.00000758753979846734], \
  PARAMETER["elt_1_1", 1.0000015503712145], \
  PARAMETER["elt_1_2", -208.185]]