[postgis-users] Getting TopologyExections when trying to node linestrings to create an overlay

[John Abraham]

Well I could say that using PostGIS ST_Intersects with "messy data" always seems to give me TopologyExceptions.  I've had luck with various combinations of ST_SnapToGrid and ST_Buffer(0), but with messy data there always seems to be some weird case that requires manually edits.  Sorry to be the bearer of bad news.  Frankly, I don't understand why the GEOS library has to throw that error. 

I would encourage you to isolate particular problems and file bug reports.  Improvements in GEOS to eliminate the underlying error(s) would certainly be welcome.  

--
John Abraham

> On Feb 8, 2015, at 1:43 PM, BladeOfLight16 <bladeoflight16 at gmail.com> wrote:
> 
> On Tue, Feb 3, 2015 at 11:28 AM, BladeOfLight16 <bladeoflight16 at gmail.com <mailto:bladeoflight16 at gmail.com>> wrote:
> I'm trying to create a polygon overlay. The basic process is relatively simple: 1) Get the boundaries 2) Union the boundaries to node the linestrings 3) Polygonize the noded outlines 4) Filter out holes using a contains or intersects test. The problem I'm running into is that I'm getting "GEOSUnaryUnion: TopologyException: found non-noded intersection between LINESTRING" errors from ST_Union. 
>  
> [a lot snipped] 
> 
> I haven't seen any response to this. I was just wondering if anyone else had a chance or intentions to look this over. Granted, it's pretty long and involved (sorry for that), but I thought all the details I included were important. I do know it went through the mailing list; someone on IRC helped me find it in the... I guess it's not the archives; I don't know what it's called. But the online browsing mechanism. Thanks to anyone who's taking a look.
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