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

[Hilmy Hashim]

I'm using OSGeo4W on Windows 7. I just checked using the OSGeo4W shell and
setting gdaldev environment epsg_tr does give me +gamma. On my Ubuntu 10.04
box with GDAL 1.7.3, the gamma is not there.

I've just updated QGis 1.7.0-114 and I don't get the gamma in the CRS
listing.

Thanks

*Hilmy*


On Thu, Apr 14, 2011 at 3:51 PM, Even Rouault
<even.rouault at mines-paris.org>wrote:

> Selon Hilmy Hashim <hilmyh at gmail.com>:
>
> > 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?
>
> I know they have updated very recently their srs.db to sync it with GDAL
> 1.8.0.
> Perhaps you should also update to the latest svn version of qgis ?
>
> A comment in the GDAL code also shows that the +gamma parameter is only
> understood by PROJ 4.8.0 (so the svn version as 4.8.0 is unreleased yet).
>
> But one thing is definitely weird and should be investigated first :
> epsg_tr.py
> -proj4 3168 *should* show the +gamma parameter (whatever your proj version
> is).
> If you don't see it, it's a clear sign you don't use GDAL 1.8.0.
>
> What does epsg_tr.py --version return ?
>
> >
> > 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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