[gdal-dev] Missing geometry type when using ogr2ogr to write FileGDB

[Stefan Keller]

Hi Jukka and Even

I also thought about this, i.e. to delay the determination of the geometry
type check to the first occurrence, in case when the abstract gml:
GeometryPropertyType has been announced in DescribeFeature.

I know that QGIS, ArcGIS Desktop and Gaia clients can read the WFS
mentioned below. And I'm almost sure they don't read the whole data stream
in order to determine that's a polygon type. It's only OGR in my test suite
which can't cope with this an needs a manual configuration ("-nlt POLYGON")
which is no option for me since it's inside an automated script.

On the other hand and from a higher level perspective something it's clear
to me: The original feature set (here e.g. svo_zonen) is of type
gml:Polygon. If the WFS doesn't expose and explain this as gml:Polygon to
others, there's a problem with this server.

Yours, Stefan


2013/4/22 Jukka Rahkonen <jukka.rahkonen at mmmtike.fi>

> Even Rouault <even.rouault <at> mines-paris.org> writes:
>
>
> >
> > Yes, when examining the
> >
> >
> "
> http://maps.zh.ch/wfs/FnsNSWFS?TYPENAME=svo_zonen&SERVICE=WFS&VERSION=1.1.0&REQUEST=DescribeFeatureType
> "
>
> > you can see :
> >
> >           <element name="msGeometry" type="gml:GeometryPropertyType"
> > minOccurs="0" maxOccurs="1"/>
> >
> > So the geometry type is undefined. OGR then reports a unknown geometry
> type.
> > There could be a mix of geometries in such a layer.
>
> Just for information, it is not uncommon that WFS servers advertise a
> general geometry type "gml:GeometryPropertyType" even the layer contains
> only one geometry type and therefore WFS clients should be aware of this.
> General geometry type comes more or less automatically when setting up a
> WFS
> service on top of Oracle because by default Oracle can hold any geometries
> in the geometry column. It is possible to set a geometry type constraint
> when creating a spatial index but it is not important for Oracle and
> therefore the constraint is often missing. Even if it exists it is a bit
> complicated to query. For example Geoserver knows how to do this check but
> GDAL OCI driver does not. If someone gets interested in improving the OCI
> driver, here is a basic part of the query.
>
> select idxmeta.sdo_layer_gtype from all_sdo_index_info idxinfo,
> all_sdo_index_metadata idxmeta
> where idxinfo.index_name=idxmeta.sdo_index_name
> and idxinfo.table_name='TABLE_NAME'
>
> If WFS client cannot handle mixed geometry types on one layer then it could
> perhaps take the first not empty geometry from the WFS response and
> initiate
> the layer to use that geometry type. To be on a safe side it might create a
> multipolygon or multilinestring layer even if the first feature is simple.
> Another geometry type appearing later in the data will lead to an error but
> it cannot be avoided anyway if client cannot handle mixed layers.
>
> -Jukka Rahkonen-
>
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