[geos-devel] Re: TopologyException makes GEOS/JTS very difficult to employ in my production environments...

G. Allegri giohappy at gmail.com
Thu Sep 30 03:27:23 EDT 2010

Hi Ragi,
I perfectly agree with you. We always pass our data through cleaning
procedures, but sometimes it fail. The example I posted wasn't
representative, because in that specific case there was effectively a
validity problem. But many times the errors happen also with valid
data, and that's the case, for example, in unioning. In such cases you
cannot know before time what kind of beasts you will get through
during the cascaded unioning. So, when I rely on valid datas, it's
difficult to explain to the customer why the system fails here and

I know I'm facing The Problem, the founmdamental one in geometrical
computing with floating point precision, and I know that also
commercial softwares suffer of similar problems. I've worked
extensively both on ArcGIS and Oracle. I've never said, and I don't
think, this is a problem of foss solutions only.


2010/9/29 Ragi Burhum <ragi at burhum.com>:
> Giovanni,
> I am actually surprised that you bring this comment about a production
> environment. When working with real data in production environment, FOSS or
> proprietary alike (i.e ESRI), I *always* encounter data that causes Topology
> Exceptions (ESRI Geometry/Geoprocessing, GEOS, JTS, whatever) at some point,
> it happens. It is just the nature of the beast - data is not perfect.
> What I do in such cases, is that before I digest the data, I have a set of
> "cleansing" and identification procedures that I put my data through before
> putting it in my pretty system. In other words, a mini-fence that I use to
> avoid problems (self intersections, nulls, multiparts, whatever).
> I apologize if this seems rude, however, the very first thing I do when a
> geometry pair gives me problems, is to look at it. That would have shown the
> problem the problem right away.
> - Ragi
>> Date: Wed, 29 Sep 2010 17:26:31 +0200
>> From: "G. Allegri" <giohappy at gmail.com>
>> Subject: Re: [geos-devel] TopologyException makes GEOS/JTS very
>>        difficult to    employ in my production environments...
>> To: GEOS Development List <geos-devel at lists.osgeo.org>
>> Howard, I know well how foss development works. So, my email wasn't
>> meant to ask someone to solve things for me. In this project I'm not
>> in the position to make such choices. I've just been able to move
>> little money to ask strk a first, basic analysis. I absolutely agree
>> with the commercial philosophy behind foss, and when I will be able to
>> manage enough money I won't easitate to invest it in that way.
>> I'm just surprised to see not so many issues raising from this
>> topology problems, as GEOS/JTS are maybe the most widespread libraries
>> used in the gfoss ecosystem. No problems when using it as a data
>> repository, but as soon as I use it massively for geometry processing
>> I face, almost everyday, thie TopolyException. So I was simply
>> wondering what the others think about this, if they have solved it
>> somehow. OS is also sharing best practices, isn'it? I don't want to
>> steal industry secrests to anyone, just share ideas...
>> Giovanni

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