Mike Leahy wrote:
Hello list,
I'm having a problem with st_difference, where two overlapping
geometries will return an empty geometrycollection, as if the do not
overlap. However, if I use st_difference on the same geometries, but
converted to EWKT, then back, then using st_difference yields the
expected output. Basically, this is what I'm getting (minus the output
coords):
# select st_astext(st_difference(g1,g2)),
st_astext(st_difference(st_asewkt(g1),st_asewkt(g2))) from temp;
st_astext | st_astext
--------------------------+-------------------------------
GEOMETRYCOLLECTION EMPTY | POLYGON(( .... ))
(1 row)
The resulting (correct) polygon is very small (a total area of
0.00048828125, using UTM coordinates), so maybe there's a problem with
that? The result of st_overlaps(g1,g2) is true for the same data that
cause this problem.
I could email someone the geometries if that would help.
Regards,
Mike
Hi Mike,
I think you'll have to post the geometries if you want someone to help
you. If they are large then place them in a text file and send it to the
list as a zipped/gzipped attachment.
Oh, and don't forget the output of "SELECT postgis_full_version()" while
you're at it :)
ATB,
Mark.
--
Mark Cave-Ayland
Sirius Corporation - The Open Source Experts
http://www.siriusit.co.uk
T: +44 870 608 0063
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