[GRASS-user] v.external problem vith postGIS data

Hi,
trying to access a polygon layer stored as a postGIS table, I ran the
v.external command (the table was itself generated by v.out.ogr). There
seems to be a problem when grass tries to build topology for the map,
and the error message is :
Random read is not supported by OGR for this layer, cannot build support

I found very few relevant information on the web for this type of error.
Has anyone coped with it yet ?

Thanks,
Vincent.

Hello Miguel,

Have you tried access the postgis table with QGis?

Yes I did, let's say it works ; but I installed Qgis in a hurry, and
there might be something wrong with PROJ : no way to set the right
coordinate system from the SRID specified in the source table.
Re-exporting the map always sets the coordinates by default in WGS 84
(srid=3344).
But at least QGis import polygons and attributes without apparent
problems...

I will try to re-compile gdal and then grass from svn. Basically I would
like my data to keep stored only as postgis tables.

I find it always easier; the polygon can be afterwards converted to a
grass polygon, shapefile or other format.

That's right. Furthermore, in my present case, QGis allows manipulation
of multipolygons, which seems impossible through grass (a future post
subject on multifeatures like multilines, geometry collections...)

Thank you,
Vincent.

Miguel

2008/11/2 Vincent Bain <bain@toraval.fr>
        Hi,
        trying to access a polygon layer stored as a postGIS table, I
        ran the
        v.external command (the table was itself generated by
        v.out.ogr). There
        seems to be a problem when grass tries to build topology for
        the map,
        and the error message is :
        Random read is not supported by OGR for this layer, cannot
        build support
        
        I found very few relevant information on the web for this type
        of error.
        Has anyone coped with it yet ?
        
        Thanks,
        Vincent.
        
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