[gdal-dev] Gamma parameter not set in proj4 string for RSO projections

[Hilmy Hashim]

Merci Even,

Didn't know which one is the effective code, there are so many versions
around. It's good to know that changes have been made.

I'm using QGis 1.7 dev and the About say it's using GDAL/OGR 1.8.0. How come
the +gamma is not included there?

Regards

*Hilmy*


On Thu, Apr 14, 2011 at 3:27 PM, Even Rouault
<even.rouault at mines-paris.org>wrote:

> Selon Hilmy Hashim <hilmyh at gmail.com>:
>
> > Sorry to bring this up again. I've been looking for why epsg_tr.py -proj4
> is
> > not including the +gamma (RectifiedToSkew angle) parameter for the
> > +proj=omerc projection as used in EPSG:3168, EPSG:3375, etc. It seems
> that
> > it is not set in
> > https://svn.osgeo.org/fdo/trunk/Thirdparty/gdal/ogr/ogr_srs_proj4.cpp:
>
> --> You are not looking to the right repository (the one above is an import
> of
> an older GDAL version by the FDO project). The main GDAL repository is
> located
> at http://svn.osgeo.org/gdal/trunk.
>
> I can see that a fix for the gamma parameter in
> http://trac.osgeo.org/gdal/changeset/18950. This is in GDAL 1.8.0 and the
> testepsg utility gives :
>
> PROJ.4 rendering of [EPSG:3168] = +proj=omerc +lat_0=4 +lonc=102.25
> +alpha=323.0
> 257905 +k=0.99984 +x_0=804670.24 +y_0=0 +gamma=323.1301023611111
> +a=6377295.664
> +b=6356094.667915204 +units=m +no_defs
>
> >
> > else if( EQUAL(pszProj,"omerc") )
> >
> >     {
> >         SetHOM( OSR_GDV( papszNV, "lat_0", 0.0 ),
> >                 OSR_GDV( papszNV, "lonc", 0.0 ),
> >                 OSR_GDV( papszNV, "alpha", 0.0 ),
> >                 0.0, /* ??? */
> >                 OSR_GDV( papszNV, "k", 1.0 ),
> >                 OSR_GDV( papszNV, "x_0", 0.0 ),
> >                 OSR_GDV( papszNV, "y_0", 0.0 ) );
> >     }
> >
> > ...
> >
> >
> >         else
> >         {
> >             sprintf( szProj4+strlen(szProj4),
> >                      "+proj=omerc +lat_0=%.16g +lonc=%.16g +alpha=%.16g"
> >                      " +k=%.16g +x_0=%.16g +y_0=%.16g ",
> >                      GetNormProjParm(SRS_PP_LATITUDE_OF_ORIGIN,0.0),
> >                      GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN,0.0),
> >                      GetNormProjParm(SRS_PP_AZIMUTH,0.0),
> >                      GetNormProjParm(SRS_PP_SCALE_FACTOR,1.0),
> >                      GetNormProjParm(SRS_PP_FALSE_EASTING,0.0),
> >                      GetNormProjParm(SRS_PP_FALSE_NORTHING,0.0) );
> >         }
> >
> > There seems to be some uncertainty about this parameter. How can this be
> > resolved and how can I help?
> >
> > Thanks.
> >
> > *Hilmy*
> >
>
>
>
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