[Qgis-developer] Qgis 1.7.4 not using '+towgs' proj parameters when OTF reprojection

Etienne Tourigny etourigny.dev at gmail.com
Fri Mar 9 08:27:59 EST 2012

.prj files lack TOWGS84 WKT

In gdal 1.9 this can be fixed with the config option GDAL_FIX_ESRI_WKT=TOWGS84
see http://www.gdal.org/ogr/classOGRSpatialReference.html#ad556dfdc04d9ec5f1714fc6b5e0eb6a6
and http://trac.osgeo.org/gdal/ticket/4345

TIcket #5066 also has more info.

On Fri, Mar 9, 2012 at 10:19 AM, Ivan Mincik <ivan.mincik at gmail.com> wrote:
> On 03/09/2012 12:31 PM, Craig Leat wrote:
>>> It seems that latest 'release-1_7' build (and most probably in 1.7.4) is
>>> not using '+towgs' proj parameters when using on-the-fly reprojection.
>>> It is visible when overlaying two layers in different projection where
>>> 'towgs' parameter is needed to reproject data accurately. Currently the
>>> error is the same as it would be without specifying 'towgs' parameter.
>>> It was working nicely in older 1.7 releases.
>> +towgs works for me on 1.7.4, but I have to specifically set the CRS
>> for the layer because it's not recognised when loading the layer. See
>> bug #5071. If you manually select the CRS from the layer properties
>> dialogue does it work?
> Craig, thanks for the answer.
> I have found that Qgis is not using 'towgs' only if using one of the
> projections from installed projection database. If I create custom
> projection by 'Settings -> Custom CRS' it is working correctly.
> To get things more clear, I am inserting missing projection (see #4945)
> to internal database before building. This projection is using 'towgs'.
> --
> Ivan Mincik
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