[GRASS-dev] Improved ellipsoid name support

Paul Kelly paul-grass at stjohnspoint.co.uk
Mon Nov 6 16:12:36 EST 2006

Yesterday I committed to CVS some updates to the gproj library that I'd 
had sitting around for ages. They do the following things:

1. When generating a WKT projection description, put the full ellipsoid 
name from ellipse.table in the "SPHEROID" section. The short name stil 
goes in the "GEOGCS" section.

2. When generating a GRASS PROJ_INFO file from an input projection 
description, try to put the ellipsoid name into the PROJ_INFO where 
possible, instead of just a and es parameters. People had complained about 
this before. The new functionality works as follows:
  a) If a datum name is specified, use the ellipsoid associated with that 
datum (i.e. ignore the ellipsoid parameters)
  b) If there is no datum specified, try and match the ellipsoid parameters 
against the known ellipsoids in ellipse.table (within a specified 
tolerance - see the code in lib/proj/convert.c around line 521; comments 
welcome) and use the first one that matches
  c) Only if a) and b) both fail, put the a and es parameters into 
PROJ_INFO directly as present

These changes should make the PROJ_INFO files generated by g.proj (and 
r.in.gdal, v.in.ogr) more like those generated by g.setproj and should 
hopefully make it more viable to use these functions as some kind of total 
replacement for g.setproj in the future (at present I'm not sure how!).


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