fix documentation and definitions of 3 grid mapping definitions
|Reported by:||etourigny||Owned by:||davidhassell|
|Keywords:||grid mapping, wkt, projection||Cc:||caron, markh|
The definitions and/or documentation for 3 grid mappings cause confusion and inconsistency when translating to/from WKT.
This ticket is the result of a discussion in the mailing list: http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2011/027605.html .
Here is a summary of suggested changes:
The 1SP (1 standard_parallel) case is not properly documented. There should be a link to http://www.remotesensing.org/geotiff/proj_list/lambert_conic_conformal_1sp.html and mention that latitude_of_projection_origin==standard_parallel (and the WKT "Scale factor at natural origin" = 1).
In the case that scale_factor is not 1, then the 2SP version should be used (as scale_factor is not part of this projection's parameters in CF).
Also, the EPSG codes should included in "Notes" (9801 for 1SP and 9802 for 2SP).
The scale_factor_at_projection_origin variant has no WKT nor PROJ.4 equivalent (they both require standard_parallel) and there are no known examples using this variant. It should be dropped from the CF spec, or at least deprecated.
The 2 variants (standard_parallel or scale_factor_at_projection_origin) are not well documented.
The standard_parallel variant corresponds to EPSG Polar Stereographic (Variant B) (EPSG dataset coordinate operation method code 9829), while the scale_factor_at_projection_origin variant corresponds to EPSG Polar Stereographic (Variant A) (EPSG dataset coordinate operation method code 9810).
This information should be included in the "Map parameters" and "Notes" sections, to be consistent with other definitions such as mercator.
Change History (11)
comment:10 Changed 3 months ago by davidhassell
- Owner changed from cf-conventions@… to davidhassell
- Status changed from new to accepted