proj_api.h access to (spheroid|other) parameters

[proj4-bot]

Reported by pramsey on 6 Feb 2012 02:09 UTC
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.

Migrated-From: https://trac.osgeo.org/proj/ticket/142

[proj4-bot]

Comment by pramsey on 6 Feb 2012 02:13 UTC
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.

[proj4-bot]

Comment by pramsey on 15 Feb 2012 23:39 UTC
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.

[proj4-bot]

Comment by warmerdam on 15 Feb 2012 23:52 UTC
Patch applied with the function name pj_get_spheroid_defn() (b52b9b99 (SVN rev2160)).

Thanks!

[proj4-bot]

Attachment added by pramsey on 8 Feb 2012 18:20 UTC
https://trac.osgeo.org/proj/attachment/ticket/142/proj_spheroid1.patch