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Ticket Resolution Summary Owner Reporter
#150 duplicate Clarification of use of standard region names in "region" variables. cf-conventions@… martin.juckes
Description

The CF standard name region has the current description "A variable with the standard name of region contains strings which indicate geographical regions. These strings must be chosen from the standard region list." This description implies that the variable should be of character type, but it is often more convenient to have an integer variable and make a clear link to the region names using flag_values and flag_meanings. The proposal is to clarify the definition so that either usage is acceptable and include an example of the latter usage in the convention text. It is also proposed that an appendix be added to the CF Convention text to state clearly any constraints on file meta-data which are implied by the CF Standard Name definitions, so that it is possible to test such constraints in the CF checker.

New description for CF standard name "region"

A variable with the standard name of region must have values associated with geographical regions from the CF standard region list, either as a character variable using the region names directly or as an integer variable with values linked to region names through flag_values and flag_meanings attributes.

New usage example in CF Convention text

The following should be placed at the end of 6.1.1, after example 6.2

A variable with standard name 'region' may also be of integer type and use 'flag_values' and 'flag_meanings' attributes to express the relationship between the integers and the region names:

integer basin(basin);
       standard_name: region;
       flag_values: '1 2 3';
       flag_meanings:'atlantic_arctic_ocean indo_pacific_ocean global_ocean';
......
values::
   basin: 1, 2, 3;

New Appendix Section

Change "Appendix B: Standard Name Table Format" to:

Appendix B: Standard Names

B.1: Standard Name Table Format

.....

and

B.2 Constraints for specific standard names

B.2.1: region

Variables with standard name region must be one of:

  • type character, with values taken from the CF standard region list;
  • type integer, with flag_values and flag_meanings attributes. The flag_meanings attributes must be a space separatd list of values from the CF standard region list (see example 6.2).
#71 fixed Correction of Vertical perspective projection davidhassell martin.raspaud
Description

Hi,

There is a confusion under the notes of the Vertical Perspective text in the conventions between geos and nsper. Snyder is describing near-sided perspective... Here is the corrected text:

Notes:

A general description of vertical perspective projection is given in [Snyder], pages 169-181.

The corresponding projection is proj.4 is nsper. This should not be confused with the proj.4 geos projection.

#72 fixed Adding the geostationary projection. davidhassell martin.raspaud
Description

There seems to be a need from the weather satellite people to add the "geos" projection to the list of projections in the CF metadata.

"geos" stands for geostationary. The projection is described in detail in the "CGMS 03, LRIT/HRIT Global specification" (Eumetsat) document. (see here also: http://remotesensing.org/geotiff/proj_list/geos.html )

A possible text for this projection is:

Geostationary projection


grid_mapping_name = geos

Map parameters:

latitude_of_projection_origin

longitude_of_projection_origin

perspective_point_height

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/geos.html . These notes assume the point of observation is directly over the equator. The projection coordinates in this projection are directly related to the scanning angle of the satellite instrument.

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