[gdal-dev] Re: Mapinfo driver does not recognise certain datums properly

[Tamas Szekeres]

Hi Devs,

Got no answer, so I call up this thread for discussion again.

In fact the approach of identifying datums by the mapinfo driver (by using
the WKT name) is quite fragile causing problems for me and for others in
the past as well, for example with the issues described in:
http://trac.osgeo.org/gdal/ticket/481
http://trac.osgeo.org/gdal/ticket/3187

In 3187 the problem was attempted to be solved by extending the lookup
table by using multiple entries for the same datum having different names.
However this approach is quite insufficient since there's no official list
of the valid WKT datum names (which may also be vendor specific) and the
datum names are also altered by gdal ie. by replacing spaces with
underscores.

The patch<http://trac.osgeo.org/gdal/attachment/ticket/481/gdal-mitab-datum-2.patch>attached
to
#481 <http://trac.osgeo.org/gdal/ticket/481> looks more compelling to me as
it seems more trivial to identify the datums by EPSG code (where exists)
and not only by the datum name.

Any objections to apply such change in gdal (mitab) at last?

Best regards,

Tamas




2012/3/15 Tamas Szekeres <szekerest at gmail.com>

> Hi Devs,
>
> I have run into a problem when assigning a spatial reference to a mapinfo
> file using ogr2ogr when using -a_srs "EPSG:28350".
> The mapinfo driver doesn't seem to recognise the datum
> (Geocentric_Datum_of_Australia_1994) and assigns WGS84 to the output file
> which is a fairly inconvenient approach.
>
> This problem is due to the incorrect entries in asDatumInfoList
> (mitab_spatialref.cpp) since the entry for
> Geocentric_Datum_of_Australia_1994 is missing, though it contains an entry
> for the projection name GDA94 (and not for the datum name).
>
> As far as I know the WKT datum names are vendor specific, therefore it's
> not quite sufficient to use as a lookop key for the datum entries. But if
> we use this approach even so, why don't we include the datum names from
> gcs.csv for being compatible with the projections constructed by GDAL
> itself?
>
> Would that be reasonable to add multiple entries in asDatumInfoList or
> placing this information in an external file?
>
> Best regards,
>
> Tamas
>
>
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