[gdal-dev] Call for discussion about RFC 61: Support for measures in geometries

[Even Rouault]

Le jeudi 04 février 2016 07:54:07, Ari Jolma a écrit :
> 03.02.2016, 16:11, Even Rouault kirjoitti:
> > Le mercredi 03 février 2016 14:36:14, Ari Jolma a écrit :
> >> I finally have the (existing) autotests passing with the new API -
> >> basically just replacing the nCoordDimension property of OGRGeometry
> >> with flags (for Z and M) - and a rather large set of tests for
> >> import/export WKT and WKB with M passing.
> > 
> > That's great !
> 
> Yes, except that I just found out that despite of the already large set
> of test WKT strings, a simple one like
> 
> GEOMETRYCOLLECTION M (POINT (1 2 3))
> 
> produces, when read in and printed out as ISO WKT
> 
> GEOMETRYCOLLECTION Z (POINT (1 2 3))
> 
> The problem is that neither OGR_G_CreateFromWkt() nor
> OGRGeometryFactory::createFromWkt does not have OGRwkbVariant
> eWkbVariant parameter (as OGRGeometryFactory::createFromWkb but not
> OGR_G_CreateFromWkb), which would at least make the case more clear in
> the code.
> 
> Reading OGC common architecture (1.2.1) it seems to me that the WKT is
> in fact invalid and it should be
> 
> GEOMETRYCOLLECTION M (POINT M (1 2 3))
> 
> Also PostGIS returns the error " can not mix dimensionality" with the
> above one.
> 
> However, interestingly, PostGIS accepts
> 
> MULTICURVE M (CIRCULARSTRING (0 0 2,1 0 2,0 0 2),(0 0 2,1 1 2))
> 
> and
> 
> MULTICURVE M (CIRCULARSTRING Z (0 0 2,1 0 2,0 0 2),(0 0 2,1 1 2))
> 
> although, in the latter one PostGIS converts the Z into M.
> 
> I think the path I'll take will be to rather easily spit out "corrupt
> data" (or a new "mixed geometries" error) for cases which involve M.

That sounds reasonable to be more strict for M.

> 
> Ari

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