[gdal-dev] vector drivers with mixed topology types in a single layer?

[Michael Sumner]

On Wed, 17 Feb 2016 11:18 pm Even Rouault <even.rouault at spatialys.com>
wrote:

> Le mercredi 17 février 2016 12:25:24, Michael Sumner a écrit :
> > Hi there, is there an easy way to discover which formats allow mixing of
> > vector types in a single layer?
>
> No, there is no such driver metadata currently. You need to open the
> dataset
> and query the layer geometry type. If it is unknown, then it allows mix of
> geometry types.
>
> >
> > I.e. a single layer MapInfo file with points, lines, and polygons - I
> know
> > there is MapInfo (tab) and MapInfo (mif) and GeoJSON,
> >
> > I'd also like to know what drivers can present as a single data set but
> > with these types separated into different layers, like SDTS.
> >
> > I consider the multiple shapefiles in one folder feature to be a somewhat
> > different, third case.
> From the point of view of the OGR API, a directory of shapefile = a dataset
> with several layers
> >
> > Is there a clear way to categorize these three kinds, and classify all
> > existing drivers this way?
>
> I think there are 2 orthogonal isssues :
> - which drivers support mixed of geometry type in a single layer
> - which drivers support multiple layers in a dataset (in general, datasets
> that support multiple layers do not set a constraint on the unicity of the
> geometry type among layers)
>
> And perhaps to address your shapefile case :
> - which drivers support only opening a file
> - which drivers support only opening a directory
> - which drivers support both
> - which drivers are not file related (already addressed by checking if the
> GDAL_DMD_CONNECTION_PREFIX / "DMD_CONNECTION_PREFIX" metadata item is
> present.
> Was added in GDAL 2.0)
>
>
>
>
> >
> > Am I on the right track, or is it more complicated?
> >
> > Cheers, Mike.
>
> --
> Spatialys - Geospatial professional services
> http://www.spatialys.com


Thank you Even, very helpful.

Cheers, Mike



> --
Dr. Michael Sumner
Software and Database Engineer
Australian Antarctic Division
203 Channel Highway
Kingston Tasmania 7050 Australia
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