proj_api.h access to (spheroid|other) parameters

[pramsey]

The current access to parameters in the projPJ is via the pj_get_def() function, which returns a string. The caller then has to parse the string for the contents (which are hopefully there) it is interested in. In high performance situations, this is not optimal, particularly since the value is just sitting in the projPJ hidden away.

I have particular need to get at the major axis and eccentricity squared of the spheroid, but in general I imagine users are interested in all manner of parameters that are stored as doubles.

[pramsey]

And unfortunately it looks like even the string returns by pj_get_def() won't do for my needs (getting the minor axis and eccentricity squared), as the spheroid information is just given using shorthands. For EPSG:4267, for example,

proj_str = +proj=longlat +datum=NAD27 +no_defs +ellps=clrk66 +nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat

Without an API to get at this information I'll be reduced to copying the PJ struct into my code to allow Proj 4.8 support once projects.h has been removed.

[pramsey]

Simple patch

[pramsey]

Yes? no? maybe so? If this goes into proj before postgis 2.0 comes out, I can ensure postgis 2.0 can read from it when proj 4.8 is released.

[warmerdam]

Patch applied with the function name pj_get_spheroid_defn() (r2160).

Thanks!