[postgis-devel] Testing ST_LineMerge issue

Mark Cave-Ayland mark.cave-ayland at siriusit.co.uk
Mon Dec 22 04:08:36 PST 2008


Kevin Neufeld wrote:

> To answer your question Mark, the OGC specs say that a LINESTRING is 
> simple if it does not pass through the same point twice.  To me, this 
> means self-intersections and perhaps coincident vertices.  At the 
> moment, PostGIS returns true for this when by rights it should be false:
> SELECT issimple('LINESTRING(0 0, 1 1, 1 1, 2 2)');
>  issimple
> ----------
>  t
> (1 row)
> 
> Something to look into?  Are coincident vertices considered to be a 
> self-intersection?

Hmmm I'm really not sure, although my intuition would say it is a 
self-intersection.


ATB,

Mark.

-- 
Mark Cave-Ayland
Sirius Corporation - The Open Source Experts
http://www.siriusit.co.uk
T: +44 870 608 0063



More information about the postgis-devel mailing list