[gdal-dev] OGR-Driver GML axis order handling (GDAL, QGIS)

[Even Rouault]

Le jeudi 13 décembre 2012 20:35:36, Jürgen Weichand a écrit :
> Hello List,
> 
> By default the OGR-Driver will swap the axis order to longitude,
> latitude for geographic coordinate systems.
> 
> "Since OGR 1.8.0, the GML driver has coordinate system support. This is
> only reported when all the geometries of a layer have a srsName
> attribute, whose value is the same for all geometries. For srsName such
> as "urn:ogc:def:crs:EPSG:", for geographic coordinate systems (as
> returned by WFS 1.1.0 for example), the axis order should be (latitude,
> longitude) as required by the standards, but this is unusual and can
> cause issues with applications unaware of axis order. So by default, the
> driver will swap the coordinates so that they are in the (longitude,
> latitude) order and report a SRS without axis order specified."
> http://www.gdal.org/ogr/drv_gml.html
> 
> 
> Example (1): urn:ogc:def:crs:EPSG::4326 - GML 3.2 (WGS 84)
> Lat / Lon is swapped to Lon / Lat by the driver (result: correct import
> into QGIS).
> http://www.weichand.de/tmp/wfs20gml32_epsg4326.gml
> 
> Example (2): urn:ogc:def:crs:EPSG::31468 - GML 3.2 (Gauß Krüger 12°)
> North / East is NOT swapped to East / North (result: incorrect import
> into QGIS).
> http://www.weichand.de/tmp/wfs20gml32_epsg31468.gml
> 
> Example (3): urn:ogc:def:crs:EPSG::25832 - GML 3.2 (ETRS89 UTM 32N)
> Default: East / North (result: correct import into QGIS).
> http://www.weichand.de/tmp/wfs20gml32_epsg25832.gml
> 
> 
> Is there any reason why OGR 1.9.2 don’t swap the coordinates of
> projected systems (to East / North)?

Yes, the reason is that it is not implemented...

There's a patch in http://trac.osgeo.org/gdal/ticket/4329 that should address 
this, but I'm not sure if this still applies cleanly to trunk, because it has 
perhaps rotten a bit.

I didn't apply since I was midly satisfied with the duplication of symbols. The 
ideal would be to have a single function that would address both 
oSRS.EPSGTreatsAsLatLong() and oSRS.EPSGTreatsAsNorthingEasting()  to avoid 
testing them in each area of the code that want to mess with axis ordering.

> 
> Thanks in advance!
> Juergen
> 
> 
> 
> Original Post @
> http://gis.stackexchange.com/questions/43896/ogr-driver-gml-axis-order-hand
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