Mapping from CF Grid Mapping Attributes to CRS WKT Elements

These provisional mappings have been compiled to support, among other things, CF proposals 69 and 80; which have been incorporated in the CF Conventions document version 1.7. If you spot any errors or omissions, please email the authors (Phil Bentley and Etienne Tourigny) or the CF mailing list, or else update this wiki page.

In Tables 1 and 2 the names of WKT PARAMETER elements follow the names of coordinate operation parameters defined in the ​ EPSG geodetic parameter registry.

The following tables list translations of projection parameter names between CF and various other representations (such as OGC WKT, EPSG and PROJ.4). The information was obtained from various sources, including http://www.remotesensing.org/geotiff/proj_list/ .

The various representations listed are:

• CF The CF-1.6 (and possibly CF-1.7) parameter names

• OGC WKT The names following OGC WKT specification (used by GDAL/OGR and CadCorp?)

• PROJ.4 The names used in the PROJ.4 software (http://trac.osgeo.org/proj/)

• EPSG The names and codes used in the EPSG Geodetic Parameter Dataset (http://www.epsg.org/ and http://www.epsg-registry.org/)

• GeoTIFF ID The names used in the GeoTIFF raster format (​http://trac.osgeo.org/geotiff/)

The following files are provided to list the various possible Datum, Ellipsoid and Prime Meridian names (in support of CF proposal 80)

• horiz_datum.csv - horizontal datum parameters for use as reference for CF-1.7 (source: GDAL/OGR, modified by Etienne Tourigny)

• ellipsoid.csv - Ellipsoid parameters from the EPSG database (source: GDAL/OGR)

• prime_meridian.csv - Prime Meridian parameters from the EPSG database (source: GDAL/OGR)

Table 1. Existing (CF-1.6) CF Grid Mapping Attributes

CF Grid Mapping Attribute	Corresponding WKT Syntax (1)
earth_radius	SPHEROID["<reference_ellipsoid_name>", <semi_major_axis>, 0.0, …​]
false_easting	PARAMETER["False easting", <value>]
false_northing	PARAMETER["False northing", <value>] grid_mapping_name no known equivalent grid_north_pole_latitude no known equivalent grid_north_pole_longitude no known equivalent inverse_flattening SPHEROID["<reference_ellipsoid_name>", <semi_major_axis>, <inverse_flattening>, …​] latitude_of_projection_origin PARAMETER["Latitude of natural origin", <value>] longitude_of_central_meridian PARAMETER["Longitude of natural origin", <value>] longitude_of_prime_meridian PRIMEM["<prime_meridian_name>", <longitude_of_prime_meridian>, …​] longitude_of_projection_origin PARAMETER["Longitude of natural origin", <value>] north_pole_grid_longitude no known equivalent perspective_point_height PARAMETER["Viewpoint height", <value>] scale_factor_at_central_meridian PARAMETER["Scale factor at natural origin", <value>] scale_factor_at_projection_origin PARAMETER["Scale factor at natural origin", <value>] semi_major_axis SPHEROID["<reference_ellipsoid_name>", <semi_major_axis>, <inverse_flattening>, …​] semi_minor_axis no direct equivalent, the SPHEROID element is used to define ellipsoid geometry standard_parallel (one parallel) PARAMETER["Latitude of standard parallel", <value>] standard_parallel (two parallels) PARAMETER["Latitude of 1st standard parallel", <value>], PARAMETER["Latitude of 2nd standard parallel", <value>] straight_vertical_longitude_from_pole PARAMETER["Longitude of origin", <value>]