[postgis-users] st_difference throws an error

Mon Nov 12 06:04:56 PST 2012

Hi,

No, it is not a bug:
Your polygons are invalid. (at least one of them)
You should always ensure you pass valid objects before calling processing
functions:

with pg as (
select 'POLYGON((-5.66666 43.53301,-5.66704 43.53335,-5.66931
43.53374,-5.66975299919511 43.533380063154,-5.66979 43.53335,-5.66971
43.53478,-5.66969091189271 43.5348058613067,-5.67026768864541
43.5374211525033,-5.67084666354158 43.5376334432986,-5.67111
43.53773,-5.67059550578171 43.53754135212,-5.66854 43.53971,-5.66854
43.53971,-5.66854 43.53971,-5.66758 43.53976,-5.6665 43.5402,-5.6665
43.5402,-5.66609712188377 43.539781395014,-5.66401 43.54013,-5.66401
43.54013,-5.66351576708437 43.5392869195307,-5.66281 43.53909,-5.6626
43.53851,-5.66159162498075 43.5369268527413,-5.66131 43.53695,-5.66196
43.53617,-5.66272791899155 43.5356642562857,-5.66378432333548
43.5344801289574,-5.66384 43.53414,-5.66452 43.53344,-5.6656
43.53337,-5.66611 43.5331,-5.66666 43.53301))'::geometry
UNION
    select 'POLYGON((-5.66577 43.53447,-5.66612 43.53455,-5.66675167677363
43.5349178897119,-5.66735 43.53529,-5.66811 43.5355,-5.66786
43.53678,-5.66816 43.53697,-5.66801 43.53717,-5.66729498033211
43.5375449497042,-5.6665 43.53782,-5.66634200990626
43.5386936730934,-5.66634 43.53876,-5.66554366174751
43.5384386684555,-5.66521 43.53856,-5.66457 43.53781,-5.6640744056249
43.5375662650614,-5.66341231504476 43.5372589777288,-5.66324
43.53718,-5.66334987968078 43.536344363177,-5.66304550704754
43.5357063513112,-5.66299 43.53559,-5.66358 43.53544,-5.66413
43.53529,-5.66521 43.535,-5.66577 43.53447,-5.66577 43.53447))'::geometry
)
select st_isvalid(geometry), st_isvalidReason(geometry) from pg;

f       "Self-intersection[-5.67084227946059 43.5376318358022]"
t       "Valid Geometry"

In addition to what Hugues said, if you are on Postgis >= 2, you can use
the very handy st_makeValid to correct geoemtries.

Nicolas

On 12 November 2012 13:57, Angel Cervera Claudio <angelcervera at silyan.com>wrote:

>  Hi Francois.
>
> This work!
>
> Could be a bug in st_difference?
>
> Thanks, Ángel
>
>
> On 12/11/12 12:42, Francois Hugues wrote:
>
> You should try the st_buffer tip :
>
> select st_astext(
>     st_difference(
>         st_buffer(st_geomfromtext('POLYGON((-5.66666 43.53301,-5.66704
> 43.53335,-5.66931 43.53374,-5.66975299919511 43.533380063154,-5.66979
> 43.53335,-5.66971 43.53478,-5.66969091189271
> 43.5348058613067,-5.67026768864541 43.5374211525033,-5.67084666354158
> 43.5376334432986,-5.67111 43.53773,-5.67059550578171
> 43.53754135212,-5.66854 43.53971,-5.66854 43.53971,-5.66854
> 43.53971,-5.66758 43.53976,-5.6665 43.5402,-5.6665
> 43.5402,-5.66609712188377 43.539781395014,-5.66401 43.54013,-5.66401
> 43.54013,-5.66351576708437 43.5392869195307,-5.66281 43.53909,-5.6626
> 43.53851,-5.66159162498075 43.5369268527413,-5.66131 43.53695,-5.66196
> 43.53617,-5.66272791899155 43.5356642562857,-5.66378432333548
> 43.5344801289574,-5.66384 43.53414,-5.66452 43.53344,-5.6656
> 43.53337,-5.66611 43.5331,-5.66666 43.53301))', 4326),0),
>        st_buffer(st_geomfromtext('POLYGON((-5.66577 43.53447,-5.66612
> 43.53455,-5.66675167677363 43.5349178897119,-5.66735 43.53529,-5.66811
> 43.5355,-5.66786 43.53678,-5.66816 43.53697,-5.66801
> 43.53717,-5.66729498033211 43.5375449497042,-5.6665
> 43.53782,-5.66634200990626 43.5386936730934,-5.66634
> 43.53876,-5.66554366174751 43.5384386684555,-5.66521 43.53856,-5.66457
> 43.53781,-5.6640744056249 43.5375662650614,-5.66341231504476
> 43.5372589777288,-5.66324 43.53718,-5.66334987968078
> 43.536344363177,-5.66304550704754 43.5357063513112,-5.66299
> 43.53559,-5.66358 43.53544,-5.66413 43.53529,-5.66521 43.535,-5.66577
> 43.53447,-5.66577 43.53447))', 4326),0)
>     )
> );
>
> Hugues.
>
>
>
>  ------------------------------
> *De :* postgis-users-bounces at lists.osgeo.org [
> mailto:postgis-users-bounces at lists.osgeo.org<postgis-users-bounces at lists.osgeo.org>]
> *De la part de* Angel Cervera Claudio
> *Envoyé :* lundi 12 novembre 2012 12:23
> *À :* postgis-users at lists.osgeo.org
> *Objet :* [postgis-users] st_difference throws an error
>
>  Hello.
>
> I post this problem in
> http://gis.stackexchange.com/questions/40872/st-difference-throws-an-errorbuy i'm sure in this mailing list people can help me.
>
> I'm retrieving "GEOSDifference: TopologyException: found non-noded
> intersection between" error when executing st_difference sql.
>
> Followed an example:
>
> Error:
>
> ERROR:  GEOSDifference: TopologyException: found non-noded intersection between LINESTRING (-5.67027 43.5374, -5.67085 43.5376) and LINESTRING (-5.67111 43.5377, -5.6706 43.5375) at -5.6708422794605911 43.537631835802237
> SQL:select st_astext(
>     st_difference(
>         st_geomfromtext('POLYGON((-5.66666 43.53301,-5.66704 43.53335,-5.66931 43.53374,-5.66975299919511 43.533380063154,-5.66979 43.53335,-5.66971 43.53478,-5.66969091189271 43.5348058613067,-5.67026768864541 43.5374211525033,-5.67084666354158 43.5376334432986,-5.67111 43.53773,-5.67059550578171 43.53754135212,-5.66854 43.53971,-5.66854 43.53971,-5.66854 43.53971,-5.66758 43.53976,-5.6665 43.5402,-5.6665 43.5402,-5.66609712188377 43.539781395014,-5.66401 43.54013,-5.66401 43.54013,-5.66351576708437 43.5392869195307,-5.66281 43.53909,-5.6626 43.53851,-5.66159162498075 43.5369268527413,-5.66131 43.53695,-5.66196 43.53617,-5.66272791899155 43.5356642562857,-5.66378432333548 43.5344801289574,-5.66384 43.53414,-5.66452 43.53344,-5.6656 43.53337,-5.66611 43.5331,-5.66666 43.53301))', 4326),
>         st_geomfromtext('POLYGON((-5.66577 43.53447,-5.66612 43.53455,-5.66675167677363 43.5349178897119,-5.66735 43.53529,-5.66811 43.5355,-5.66786 43.53678,-5.66816 43.53697,-5.66801 43.53717,-5.66729498033211 43.5375449497042,-5.6665 43.53782,-5.66634200990626 43.5386936730934,-5.66634 43.53876,-5.66554366174751 43.5384386684555,-5.66521 43.53856,-5.66457 43.53781,-5.6640744056249 43.5375662650614,-5.66341231504476 43.5372589777288,-5.66324 43.53718,-5.66334987968078 43.536344363177,-5.66304550704754 43.5357063513112,-5.66299 43.53559,-5.66358 43.53544,-5.66413 43.53529,-5.66521 43.535,-5.66577 43.53447,-5.66577 43.53447))', 4326)
>     )
> );
>
> In gis.stackexchange.com i attached images with various shapes with this problem. All share a common pattern. Some parts of edge are near to be parallel.
>
>
> How to resolve this problem? Is a bug?
>
> Thanks!
>
>
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