wiki:GridMapNames

Version 12 (modified by edavis, 6 years ago) (diff)

Fixed Mercator: add false easting and northing, remove latitude of projection origin.

Grid Mapping: Adding new grid mappings

Title

Add new grid mappings to the existing list.

Requirement

A number of grid mappings are being used that are not listed in CF. Make additions to the existing list.

This is a follow-up proposal to the proposal in CF Trac ticket #18.

Summary of Change

Add new grid mappings and required attributes.

Existing:

  • Albers Conic Equal Area (EPSG 9822)
  • Azimuthal Equidistant (EPSG 9832)
  • Lambert Azimuthal Equal Area (EPSG 9820)
  • Lambert Conformal Conic (EPSG 9801 for one standard parallel, EPSG 9802 for two standard parallels)
  • Latitude-Longitude (???)
  • Polar Stereographic (EPSG 9810)
  • Rotated Pole
  • Stereographic (EPSG 9809)
  • Transverse Mercator (EPSG 9807)
  • Vertical Perspective (EPSG 9838, EPSG 9839 special case for view point height approaching or at infinity)

To be added:

  • Lambert Cylindrical Equal Area (EPSG 9834 for spherical earth, EPSG 9835)
  • Mercator (EPSG 9804 for one standard parallel, EPSG 9805 for two standard parallels)
  • Orthographic (EPSG 9840)

Benefit

Allow existing data using non-CF defined grid mappings to be CF compliant.

Status Quo

CF compliant data using grid mappings that are not supported by CF.

Initial Statement of Technical Proposal

Add Examples to Appendix F

Lambert Cylindrical Equal Area

grid_mapping_name = lambert_cylindrical_equal_area
Map parameters:
  • longitude_of_central_meridian
  • Either standard_parallel or scale_factor_at_projection_origin
  • false_easting
  • false_northing
Map coordinates:

The x (abscissa) and y (ordinate) rectangular coordinates are identified by the standard_name attribute value projection_x_coordinate and projection_y_coordinate respectively.

Notes:

Notes on using the PROJ.4 software packages for computing the mapping may be found at http://www.remotesensing.org/geotiff/proj_list/cylindrical_equal_area.html ("Lambert Cylindrical Equal Area" or EPSG 9834 or EPSG 9835). Detailed formulas can be found in [Snyder] pages 76-85.

Mercator

grid_mapping_name = mercator
Map parameters:
  • longitude_of_projection_origin
  • Either standard_parallel (EPSG 9805) or scale_factor_at_projection_origin (EPSG 9804)
  • false_easting
  • false_northing
Map coordinates:

The x (abscissa) and y (ordinate) rectangular coordinates are identified by the standard_name attribute value projection_x_coordinate and projection_y_coordinate respectively.

Notes:

Notes on using the PROJ.4 software packages for computing the mapping may be found at http://www.remotesensing.org/geotiff/proj_list/mercator_1sp.html ("Mercator (1SP)" or EPSG 9804) or http://www.remotesensing.org/geotiff/proj_list/mercator_2sp.html ("Mercator (2SP)" or EPSG 9805).

More information on formulas available in [OGP/EPSG_GN7_2].

Orthographic

grid_mapping_name = orthographic
Map parameters:
  • longitude_of_projection_origin
  • latitude_of_projection_origin
  • false_easting
  • false_northing
Map coordinates:

The x (abscissa) and y (ordinate) rectangular coordinates are identified by the standard_name attribute value projection_x_coordinate and projection_y_coordinate respectively.

Notes:

Notes on using the PROJ.4 software packages for computing the mapping may be found at http://www.remotesensing.org/geotiff/proj_list/orthographic.html ("Orthographic" or EPSG 9840).

More information on formulas available in [OGP/EPSG_GN7_2].

Add to References

[OGP/EPSG_GN7_2] "OGP Surveying and Positioning Guidance Note 7, part 2: Coordinate Conversions and Transformations including Formulas", OGP/EPSG.