Updated pj_ellps.c with non-Earth planetary ellipsoids

[cirquelar]

I updated the file pj_ellps.c to contain the non-Earth planetary ellipsoids (e.g. Mars) with the appropriate semi-major axis (a) and semi-minor axis (b) or reciprocal flattening (rf) parameters (attached).

All values are derived from the latest pertinent report (in 2000) provided by the International Astronomical Union (IAU) Working Group (IAU/IAG WG) on Cartographic Coordinates and Rotational Elements. The reference for the report is "Report of the IAU/IAG Working Group on Cartographic Coordinates and Rotational Elements of the Planets and Satellites: 2000," by P. K. Seidelmann, et al., now published in Celestial Mechanics and Dynamical Astronomy, 82, pp. 83-110, 2002. A preprint with the values is available here:  http://astrogeology.usgs.gov/Projects/ISPRS/PREPRINTS/IAU2000/IAU2000_preprint.pdf.

These values match the default ESRI ArcGIS 9.3.1 projection files for geographic coordinate systems for the solar system (C:\Program Files\ArcGIS\Coordinate Systems\Geographic Coordinate Systems\Solar System). I did not update the pj_datums.c file as there are not multiple datums for any of the planetary bodies.

While PROJ.4 can work with non-Earth coordinate systems via specifying the semi-major axis, reciprocal flattening and appropriate projection elements (e.g. latitude of true scale), this addition will standardize the ellipsoid sizes on peer-reviewed values and assist scientists working with this software to conduct planetary research.

[warmerdam]

This is not release critical for 4.8.0. In general I am not too keen on extending the built in lists of named ellipsoids, datums, etc. Initialization files are (imho) a better solution for such definitions.