[gdal-dev] ISO WKB

[Paul Ramsey]

Back to this, is it OK? How are we patching back to SVN? I can convert
it into a patch and attach to a ticket, if that's the path.

P.

On Fri, Dec 13, 2013 at 12:00 PM, Paul Ramsey <pramsey at cleverelephant.ca> wrote:
> I’ve pushed up some work to do this
>
> https://github.com/pramsey/gdal/tree/isowkb
>
> I had to change *two* method signatures, which I don’t really like, both
> exportToWkb and getGeometryType needed a variant parameter added. The
> problem is that getGeometryType returns the full WKB type, with
> dimensionality encoded, which makes it somewhat duplicative of
> getCoordinateDimension. In an ideal world, getGeometryType would only return
> the type number, and dimensionally information would be inferred from
> getCoordinateDimension.
>
> Then only the exportToWkb signature would need a variant parameter.
>
> importFromWkb also was changed to ingest the ISO variant if that’s what it’s
> fed. No changes to signature required there.
>
> P.
>
> --
> Paul Ramsey
> http://cleverelephant.ca
> http://postgis.net
>
> On December 12, 2013 at 2:58:05 PM, Even Rouault
> (even.rouault at mines-paris.org) wrote:
>
> Le jeudi 12 décembre 2013 23:39:25, Paul Ramsey a écrit :
>> I’ve been looking over the code, and I think I can make importFromWkb
>> consume ISO inputs with relatively minor changes. (during the geometry
>> type determination in the concrete types, it looks easy enough to add a
>> little logic to deal with ISO type numbers) For exportToWkb, I’m wondering
>> if maybe an optional parameter (wkbVariant?) that defaults to
>> wkbVariantOGC would be sufficient?
>
> Sounds good to me. Is "wkbVariantOGC" the variant currently implemented ? Is
> our 3D support really compliant with an OGC standard ?
>
>>
>> It also seems the wkb reader/writer have little handling for empty
>> geometry
>> types. I’d like to add some in, if that’s OK.
>
> Are you sure about that ?
>
> See :
>
>>>> from osgeo import ogr
>>>> ogr.CreateGeometryFromWkb(g.ExportToWkb()).ExportToWkt()
> 'LINESTRING EMPTY'
>>>> ogr.CreateGeometryFromWkb(ogr.CreateGeometryFromWkt('LINESTRING
> EMPTY').ExportToWkb()).ExportToWkt()
> 'LINESTRING EMPTY'
>>>> ogr.CreateGeometryFromWkb(ogr.CreateGeometryFromWkt('LINESTRING
> EMPTY').ExportToWkb()).ExportToWkt()
> 'LINESTRING EMPTY'
>>>> ogr.CreateGeometryFromWkb(ogr.CreateGeometryFromWkt('POLYGON
> EMPTY').ExportToWkb()).ExportToWkt()
> 'POLYGON EMPTY'
>>>> ogr.CreateGeometryFromWkb(ogr.CreateGeometryFromWkt('MULTILINESTRING
> EMPTY').ExportToWkb()).ExportToWkt()
> 'MULTILINESTRING EMPTY'
>>>> ogr.CreateGeometryFromWkb(ogr.CreateGeometryFromWkt('MULTIPOLYGON
> EMPTY').ExportToWkb()).ExportToWkt()
> 'MULTIPOLYGON EMPTY'
>>>> ogr.CreateGeometryFromWkb(ogr.CreateGeometryFromWkt('GEOMETRYCOLLECTION
> EMPTY').ExportToWkb()).ExportToWkt()
> 'GEOMETRYCOLLECTION EMPTY'
>
> The only exception is POINT EMPTY due to the lack of wkb representation for
> it
> :
>>>> ogr.CreateGeometryFromWkb(ogr.CreateGeometryFromWkt('POINT
> EMPTY').ExportToWkb()).ExportToWkt()
> 'POINT (0 0)'
>
>
>>
>> Fortunately the only substantial difference for ISO WKB is the type
>> number.
>>
>> I’m starting an isowkb branch on my git repo to hold this piece of work, I
>> don’t think it’ll be very big.
>>
>> Then I’ll start asking about ‘m’ dimensions :)
>
> That's a fresh new land to explore...
>
>>
>> P.
>>
>> --
>> Paul Ramsey
>> http://cleverelephant.ca
>> http://postgis.net
>>
>> On December 12, 2013 at 2:33:41 PM, Even Rouault
>> (even.rouault at mines-paris.org) wrote:
>>
>> Le jeudi 12 décembre 2013 21:36:42, Paul Ramsey a écrit :
>> > Hey all,
>> > Is there already a facility for writing out ISO-standard WKB in GDAL?
>> > The
>> > biggest difference is the wkbGeometryType number for the case of 3d
>> > features. OGR currently uses the old extended SFSQL adopted by PostGIS.
>> > ISO (naturally) did their own thing. As far as I can see, there’s no
>> > support there now, or is there? P.
>>
>> Hi Paul,
>>
>> no, there's no support for ISO WKB yet. We still stick to
>> http://home.gdal.org/projects/opengis/twohalfdsf.html
>>
>> I can imagine we could have exportToISOWkb() method in OGRGeometry*. Or we
>> could add an extra boolean argument bISOWkb to the existing exportToWkb().
>> Not sure about WkbSize() : does the size of ISO WKB blobs differ from the
>> unofficial WKB ?
>>
>> Even
>>
>> --
>> Geospatial professional services
>> http://even.rouault.free.fr/services.html
>
> --
> Geospatial professional services
> http://even.rouault.free.fr/services.html