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<DIV><FONT face=Arial size=2>Hello Postgis Users,</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>we are building a complex application with many gis
operations.<BR>The most problems occured within the geomUnion, intersection and
difference functions.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>We have some different problems using GEOS
operations. We think that is a <BR>problem with tolerances while processing the
geometries.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>We have tried "SnapToGrid","Buffer" with zero
distance and so on ... , but we can't find a<BR>solution that will work in all
cases.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>Either we get an Error from Geos (eg. "No outgoing
edge found" and many more), or we dont get the <BR>expected result.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>The following example creates two different results
for the same operation with the<BR>"same" geometries, but different geometrie
casts.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>----- import with psql
-----------------------------------------------</FONT></DIV>
<DIV> </DIV><FONT face=Arial size=2>
<DIV><BR>CREATE TABLE t1 (<BR> geom
public.geometry<BR>);<BR>COPY t1 (geom) FROM
stdin;<BR>01030000000100000008000000F326BCE75EA9544154B30FE548955541D31C05585EA9544149A605194A9555413D0AD7B35CA9544185EB5118489555415C8FC2655CA95441333333C347955541295C8FD25CA9544185EB516847955541EC51B81E5DA954410AD7A3C0479555410AD7A3A05DA954416666665647955541F326BCE75EA9544154B30FE548955541<BR>01030000000100000005000000D41C05585EA9544148A605194A955541F326BCE75EA9544154B30FE5489555418FC2F5685FA95441295C8F8249955541C3F5287C5EA9544152B81E454A955541D41C05585EA9544148A605194A955541<BR>\.<BR> <BR>--
the statement below will produce a single-polygon with 10 Points, <BR>-- this is
the expected result ...<BR>select asText(geomUnion(asText(geom))) from t1</DIV>
<DIV> </DIV>
<DIV><BR>-- but this statement produces a multipolygon with 13 points <BR>select
asText(geomUnion(geom)) from t1 </DIV>
<DIV> </DIV>
<DIV> <BR>-- Postgres Version : "PostgreSQL 8.1.2 on i686-pc-mingw32,
compiled by GCC gcc.exe (GCC) 3.4.2 (mingw-special)"<BR>-- Postgis Version
: "POSTGIS="1.1.1" GEOS="2.2.1-CAPI-1.0.1" PROJ="Rel. 4.4.9, 29 Oct 2004"
USE_STATS (procs 1.1.0 upgrade)" <BR>-- OS: Windows Server
2003</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><SPAN class=622472218-11042006><FONT face=Arial size=2>-- Best regards
</FONT></SPAN></DIV>
<DIV class=Section1>
<P><SPAN style="FONT-SIZE: 7.5pt; COLOR: navy; FONT-FAMILY: Arial"><SPAN
class=622472218-11042006> </SPAN>__________________________________________________________________<?xml:namespace
prefix = o ns = "urn:schemas-microsoft-com:office:office"
/><o:p></o:p></SPAN></P>
<P><SPAN style="FONT-SIZE: 7.5pt; COLOR: navy; FONT-FAMILY: Arial">Rene
Neidt<BR>Projektleiter Software<BR>IDU Ingenieurgesellschaft für
Datenverarbeitung und Umweltschutz mbH<BR>Theodor-Körner-Allee 16<BR>02763
Zittau<BR>Germany<o:p></o:p></SPAN></P>
<P><SPAN style="FONT-SIZE: 7.5pt; COLOR: navy; FONT-FAMILY: Arial">Tel ++49 3583
61-15-37<BR>Fax ++49 3583 61-12-10<o:p></o:p></SPAN></P>
<P><SPAN style="FONT-SIZE: 7.5pt; COLOR: navy; FONT-FAMILY: Arial">Internet
</SPAN><U><SPAN
style="FONT-SIZE: 7.5pt; COLOR: blue; FONT-FAMILY: Arial">http://www.idu.de/</SPAN></U><SPAN
style="FONT-SIZE: 7.5pt; COLOR: navy; FONT-FAMILY: Arial">, </SPAN><U><SPAN
style="FONT-SIZE: 7.5pt; COLOR: blue; FONT-FAMILY: Arial">http://www.webmapserver.de/<BR></SPAN></U><SPAN
style="FONT-SIZE: 7.5pt; COLOR: navy; FONT-FAMILY: Arial">Anfahrt:
</SPAN><U><SPAN style="FONT-SIZE: 7.5pt; COLOR: blue; FONT-FAMILY: Arial"><A
href="http://www.stadtplan-zittau.de/?alias=idu">http://www.stadtplan-zittau.de/?alias=idu</A><o:p></o:p></SPAN></U></P></DIV>
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