[postgis-users] ST_within bug?

[Johannes Sommer]

Hi Paul,

The update worked. Now I get the correct boolean values. But my problem 
is not solved.
As I wrote the problem is that the Desktop Client tries to insert a 
geometry object as GeometryFromText in a way that results in a slightly 
different binary geometry object.

example:
application (Kosmo) insert:
7;"0103000020EC7A000001000000060000007101EE208F2E51416E <----
252C38668A5441320DDB8DF62F514174604A3E2E8A544154E6C014F52F514164A38519888A54418CAB1FB4132F5141C4<---
F318A8BB8A54415<---
36F90B2A62E514125384224A18A54417101EE208F2E51416E252C38668A5441"

after update in psql-terminal (ST_GeomFromText...):
7;"0103000020EC7A000001000000060000007001EE208F2E51416D <----
252C38668A5441370DDB8DF62F514176604A3E2E8A54414FE6C014F52F514163A38519888A54418CAB1FB4132F5141C2<---
F318A8BB8A54414<---
E6F90B2A62E514129384224A18A54417001EE208F2E51416D252C38668A5441"


I'm not sure, but I think Kosmo uses "GeometryFromText" (I have asked 
the list for this).
I could not reproduce the reaction in a psql terminal with 
"GeometryFromText". If I do the INSERTS on the terminal, I get the 
correct results.

Can this happen if one uses (GeometryFromText, SRID) instead of 
(ST_GeomFromText, SRID) in an application with JDBC-Driver?

thanks,
Johannes


Paul Ramsey schrieb:
> I think your geometries have slightly different topology than your 
> text representations admit. I cannot reproduce your result, but then I 
> started from your text representations.
>
> Do this:
>
> update test set geometry = ST_GeomFromText('POLYGON((4506577.35665529 
> 5381992.48407281,4506597.92548351 5381745.65813424,4506999.01763368 
> 5381784.22468715, 4506834.46700796 5382069.61717861,4506615.92320819 
> 5382085.04379977,4506577.35665529 5381992.48407281))', 31468) where 
> t_id = 3;
>
> And then see what happens.
>
> On Feb 13, 2008, at 3:44 AM, Johannes Sommer wrote:
>
>> Hi,
>>
>> I ve got a problem with the ST_Within() function. It does not always 
>> return correct answers.
>>
>> SELECT AsText(geometry) FROM test WHERE t_id=3;
>> -->result:
>> "POLYGON((
>> 4506577.35665529 5381992.48407281,
>> 4506597.92548351 5381745.65813424,
>> 4506999.01763368 5381784.22468715,
>> 4506834.46700796 5382069.61717861,
>> 4506615.92320819 5382085.04379977,
>> 4506577.35665529 5381992.48407281))"
>>
>> -- (WKT/WKB):
>> SELECT ST_Within(ST_GeomFromText('POLYGON((
>> 4506577.35665529 5381992.48407281,
>> 4506597.92548351 5381745.65813424,
>> 4506999.01763368 5381784.22468715,
>> 4506834.46700796 5382069.61717861,
>> 4506615.92320819 5382085.04379977,
>> 4506577.35665529 5381992.48407281))', 31468), a.geometry) FROM test a 
>> WHERE t_id=3;
>>
>> -->result: false (but obviously it should be true)
>>
>> -- (WKT/WKT):
>>
>> SELECT ST_Within(ST_GeomFromText('POLYGON((
>> 4506577.35665529 5381992.48407281,
>> 4506597.92548351 5381745.65813424,
>> 4506999.01763368 5381784.22468715,
>> 4506834.46700796 5382069.61717861,
>> 4506615.92320819 5382085.04379977,
>> 4506577.35665529 5381992.48407281))', 31468), (SELECT 
>> AsText(geometry) FROM test WHERE t_id=3));
>>
>> --> result:
>> ERROR: Operation on two geometries with different SRIDs
>> KONTEXT: SQL function "st_within" statement 1
>>
>> Ok - I understand this reaction, because AsText returns no SRID.
>>
>> -- (WKT/WKT):
>> SELECT ST_Within((select st_astext(geometry) FROM test WHERE t_id=3), 
>> (SELECTst_astext(geometry) FROM test WHERE t_id=3));
>>
>> -->result: true (as it should be)
>>
>> -- (WKB/WKB):
>> select st_within((SELECT geometry FROM test WHERE t_id=3), (SELECT 
>> geometry FROM test WHERE t_id=3));
>> -->result: true (correct)
>>
>> SELECT ST_Within((select st_astext(geometry) FROM test WHERE t_id=3), 
>> (SELECTst_astext(geometry) FROM test WHERE t_id=3));
>>
>> So the problem is that the Desktop Client tries to insert a geometry 
>> object as GeometryFromText / ST_GeomFromText / GeomFromText
>> and I have to compare this new geometry object with an existing Polygon.
>>
>> It makes no difference if I use _st_within / st_within / within, 
>> geometryfromtext / st_geomfromtext / geomfromtext or astext / st_astext.
>>
>> I used:
>> -Windows XP, "POSTGIS="1.3.1" GEOS="3.0.0rc4-CAPI-1.3.3" PROJ="Rel. 
>> 4.5.0, 22 Oct 2006" USE_STATS",
>> "PostgreSQL 8.2.5 on i686-pc-mingw32, compiled by GCC gcc.exe (GCC) 
>> 3.4.2 (mingw-special)"
>>
>> -Linux, "POSTGIS="1.3.2" GEOS="3.0.0rc5-CAPI-1.4.0" PROJ="Rel. 4.6.0, 
>> 21 Dec 2007" USE_STATS",
>> "PostgreSQL 8.2.6 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 
>> 4.2.1 (SUSE Linux)"
>>
>> Where am I going wrong?
>>
>> regards,
>> Johannes
>>
>>
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