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:

• 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

Mercator

grid_mapping_name = mercator

Map parameters:

• longitude_of_projection_origin
• latitude_of_projection_origin
• Either standard_parallel or scale_factor_at_projection_origin
• standard_parallel - There may be 1 or 2 values.

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).

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).