[gdal-dev] New capabilities in OGR VRT : OGRVRTWarpedLayer and OGRVRTUnionLayer
Even Rouault
even.rouault at mines-paris.org
Sun Jul 1 13:51:34 PDT 2012
Hi,
FYI, I've just commited into trunk a few extensions to the OGR VRT syntax.
In addition to the existing <OGRVRTLayer>, <OGRVRTDataSource> can now accept :
- a <OGRVRTWarpedLayer> child to do on-the-fly reprojection of a base layer
- a <OGRVRTUnionLayer> to do on-the-fly concatenation of several base layers.
Examples from the updated http://gdal.org/ogr/drv_vrt.html :
"""
Example: Reprojected layer (GDAL >= 2.0.0)
The following example will return the source.shp layer reprojected to
EPSG:4326.
<OGRVRTDataSource>
<OGRVRTWarpedLayer>
<OGRVRTLayer name="source">
<SrcDataSource>source.shp</SrcDataSource>
</OGRVRTLayer>
<TargetSRS>EPSG:4326</TargetSRS>
</OGRVRTWarpedLayer>
</OGRVRTDataSource>
Example: Union layer (GDAL >= 2.0.0)
The following example will return a layer that is the concatenation of
source1.shp and source2.shp.
<OGRVRTDataSource>
<OGRVRTUnionLayer name="unionLayer">
<OGRVRTLayer name="source1">
<SrcDataSource>source1.shp</SrcDataSource>
</OGRVRTLayer>
<OGRVRTLayer name="source2">
<SrcDataSource>source2.shp</SrcDataSource>
</OGRVRTLayer>
</OGRVRTUnionLayer>
</OGRVRTDataSource>
"""
The unioning capability can also be used in OGR SQL, for example :
"SELECT * FROM first_layer UNION ALL SELECT * FROM second_layer"
Best regards,
Even
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