[Qgis-developer] SRS DB maintenance

[Radim Blazek]

Note. The database from epsg.org does contain the correct
transformations (towgs84) 4836 (SK) and 5239 (CZ), the problem is that
each one is for a different territory but the same CRS. While the
relation between CRS and transformation in EPSG database is
(naturally) one-to-many, QGIS oversimplified the relation to
one-to-one. So all the evil comes from QGIS itself. We should probably
separate CRS from towgs84 and allow users to choose from multiple
towgs84 for CRS.

Radim

On Thu, Jul 4, 2013 at 11:00 AM, Radim Blazek <radim.blazek at gmail.com> wrote:
> On Thu, Jul 4, 2013 at 8:59 AM, Jürgen E. <jef at norbit.de> wrote:
>> 7805af3cf introduces a noupdate field in tbl_srs, that is set to 1 for the
>> mentioned CRSes.  And crssync doesn't update or delete records marked like
>> that.
>
> Great, thanks.
>
>> But that flag should probably tracked somehow and set to 0 eventually,
>> when the CRSes get corrected in/introduced to geotiff/GDAL/proj.4.
>
> It seems that GDAL is occasionally synced with EPSG from libgeotif
> [1], no additional overrides. In [2] is described EPSG in libgeotif.
> They keep overrides separate in gcs.override.csv and pcs.override.csv,
> it is not clear to me if gcs/pcs.override.csv are used somehow by
> crssync or not.
>
> If I got it,  If we want to get correct towgs84 params to srs.db in a
> clean way, they must be added to libgeotif gcs/pcs.override.csv and
> crssync must use them.
>
> BTW, we have a problem [2]:
>
> "Note that we deliberately keep alterations separate from the EPSG definitions
> in gcs.csv and pcs.csv to avoid violating the EPSG distribution license
> which requires that the definitions be distributed in unaltered form."
>
> Radim
>
> [1] http://trac.osgeo.org/gdal/log/trunk/gdal/data/pcs.csv
> [2] http://svn.osgeo.org/metacrs/geotiff/trunk/libgeotiff/csv/README
>
>>
>> Jürgen
>>
>> [1] http://en.wikipedia.org/wiki/DWIM
>>
>> --
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>> committ(ed|ing) to QGIS                                IRC: jef on FreeNode
>>
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