[postgis-users] function difference(geometry, geometry) throws an exception

[toni hernnadez]

HI,

If I execute the sql that follows I got the error:

NOTICE:  TopologyException: side location conflict (498355,651613,651613)
ERROR:  GEOS difference() threw an error!

Does anyone know what this means?

I use buffer, intersection and diference functions. All in the same sql
I have tested this in postgis version 1.1 and 1.0.
This is the sql hat throws the exception is this one:

select astext(difference(

(GeomFromText('POLYGON((498356.421005198 
651606.895014999,498352.452255198 651623.299181666,498370.708505198 
651634.940848333,498405.898088531 651651.080431666,498441.616838531 
651665.367931666,498469.662671864 651680.713764999,498473.631421864 
651670.130431666,498479.716838531 651644.465848333,498488.183505198 
651612.451264999,498468.339755198 651603.190848333,498387.112671864 
651566.149181666,498374.412671864 651562.709598333,498372.562028232 
651563.436636902,498372.785232024 651564.01338174,498372.987592376 
651565.172049121,498372.960019638 651566.347931579,498370.049602971 
651590.160431579,498369.952570713 651590.594769057,498369.986735951 
651590.441838025,498369.952368124 651590.728125827,498369.858822152 
651591.014407994,498369.793156749 651591.308340611,498369.676598025 
651591.572075168,498369.587038588 651591.846157196,498361.914121922 
651609.308657196,498361.337694991 651610.333933648,498360.572322429 
651611.227054386,498359.647417073 651611.953697279,498358.598522519 
651612.485937849,498357.465947195 651612.80332239,498356.293215336 
651612.893653991,498355.12539437 651612.753461259,498355.01255936 
651612.716591129,498356.421005198 651606.895014999))',23031))

,

(select       
    intersection(
        (select buffer(geomfromtext('LINESTRING(498356.421005198 
651606.895014999,498352.452255198 651623.299181666)',23031),6))
        ,
        (GeomFromText('POLYGON((498356.421005198 
651606.895014999,498352.452255198 651623.299181666,498370.708505198 
651634.940848333,498405.898088531 651651.080431666,498441.616838531 
651665.367931666,498469.662671864 651680.713764999,498473.631421864 
651670.130431666,498479.716838531 651644.465848333,498488.183505198 
651612.451264999,498468.339755198 651603.190848333,498387.112671864 
651566.149181666,498374.412671864 651562.709598333,498372.562028232 
651563.436636902,498372.785232024 651564.01338174,498372.987592376 
651565.172049121,498372.960019638 651566.347931579,498370.049602971 
651590.160431579,498369.952570713 651590.594769057,498369.986735951 
651590.441838025,498369.952368124 651590.728125827,498369.858822152 
651591.014407994,498369.793156749 651591.308340611,498369.676598025 
651591.572075168,498369.587038588 651591.846157196,498361.914121922 
651609.308657196,498361.337694991 651610.333933648,498360.572322429 
651611.227054386,498359.647417073 651611.953697279,498358.598522519 
651612.485937849,498357.465947195 651612.80332239,498356.293215336 
651612.893653991,498355.12539437 651612.753461259,498355.01255936 
651612.716591129,498356.421005198 651606.895014999))',23031)
        )
    )
)

)
)