[postgis-users] Grouping by geom with count?

[Rémi Cura]

Hey,
if you look at the error you get :
LINESTRING (530395 178004, 530396 178004) and
LINESTRING (530396 178004, 530396 178004)
at (530395.54888857342, 178004.12613484744)

You see there is no reason to output this error, in fact those two
linestring intersect only on (530396 178004),
yet geos thinks they intersect on (530395.54888857342, 178004.12613484744).

First the second linestring is not a line, but  a point ! (or it could be a
line so small geos thinks it's a point, aka numerical error).
(Have you chekced all your input geometry are valid (ST_IsValid())  )

Now if you translate, geos will try to compute on

LINESTRING (395 4, 396 4) and
LINESTRING (396 4, 396 4)
You see it is much easier for him ^^

And yes snapping could help too
(in fact it is mandatory in some case)

Cheers,
Rémi-C
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/postgis-users/attachments/20140428/9d1387cc/attachment.html>