[Gdal-dev] Intersection of two OGRLinearRing objects is NULL

[Mateusz Loskot]

Dmitry Kan wrote:
> Hello list!
> 
> I have two polygons. I know that their exterior rings intersect in two
> OGRPoint's. Despite that fact Intersection() on the ring objects return
> NULL;

Dmitry,

I did short test:
I changed LINEARRING to LINESTRING because it's not possible to create
LINEARRING directly from WKT. Note, that LINEARRING should not be used
as standalone geometry but it's a variation of LINESTRING used to
support POLYGON geometries.
Next, I created two geometries and generated intersection.
The intersection operation succeeded and resulting geometry is of type
of 4, it is MultiPoint:

>>> import ogr
>>> a = open('a.txt').read()
>>> g1 = ogr.CreateGeometryFromWkt(a)
>>> g1.GetGeometryType()
2
>>> b = open('b.txt').read()
>>> g2 = ogr.CreateGeometryFromWkt(b)
>>> g2.GetGeometryType()
2
>>> ints = g1.Intersection(g2)
>>> print ints.GetGeometryType()
4

Files a.txt and b.txt consist of definition of your geometries.
I used GDAL from current SVN.

Cheers
-- 
Mateusz Loskot
http://mateusz.loskot.net