'[postgis-users] st_intersection error/bug?'

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List:       postgis-users
Subject:    [postgis-users] st_intersection error/bug?
From:       DÃ¼ster_Horst <Horst.Duester () bd ! so ! ch>
Date:       2009-08-28 10:39:20
Message-ID: H00002eb0568c9e3.1251455959.srsofaioi6145.ktso.ch () MHS
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I do have 2 simple linestrings which partly have the same geometry (see
attached dump and image). My aim is to detect the common part of these
two linestrings with the following query:

select st_intersection(a.the_geom, b.the_geom), a.myid
from aline1, aline2

But as the result I get a geometrycollection with one POINT and one
LINESTING. I expected one linestring. Is it a bug??
I'll appreciate any hints.

My system:
Postgis 1.4.0
Geos 3.1.1
Postgres 8.3.6

Best regards

Dr. Horst Düster
Stv. Amtschef / GIS-Koordinator 

Kanton Solothurn
Bau- und Justizdepartement
Amt für Geoinformation
SO!GIS Koordination
Rötistrasse 4
CH-4501 Solothurn

Telefon ++41(0)32 627 25 32
Telefax ++41(0)32 627 22 14

mailto:horst.duester@bd.so.ch
http://www.agi.so.ch

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<body>
<div class="Normal"><span style='font-size: 10pt; '>I do have 2 simple
linestrings which partly have the same geometry (see attached dump and image).
My aim is to detect the common part of these two linestrings with the following
query:</span></div>
<br>
<div class="Normal"><span style='font-size: 10pt; '>select
st_intersection(a.the_geom, b.the_geom),
a.myid</span><br><span style='font-size: 10pt; '>from aline1,
aline2</span></div>
<br>
<div class="Normal"><span style='font-size: 10pt; '>But as the result I get a
geometrycollection with one POINT and one LINESTING. I expected one linestring.
Is it a bug??</span><br><span style='font-size: 10pt; '>I'll appreciate any
hints.</span></div>
<br>
<div class="Normal"><span style='font-size: 10pt; '>My
system:</span><br><span style='font-size: 10pt; '>Postgis
1.4.0</span><br><span style='font-size: 10pt; '>Geos
3.1.1</span><br><span style='font-size: 10pt; '>Postgres 8.3.6</span></div>
<br>
<div class="Normal"><span style='font-size: 10pt; '>Best regards</span></div>
<br>
<div class="Normal"><span style='font-size: 10pt; '>Dr. Horst
D&uuml;ster</span><br><span style='font-size: 10pt; '>Stv. Amtschef /
GIS-Koordinator </span></div>
<br>
<div class="Normal"><span style='font-size: 10pt; '>Kanton
Solothurn</span><br><span style='font-size: 10pt; '>Bau- und
Justizdepartement</span><br><span style='font-size: 10pt; '>Amt f&uuml;r
Geoinformation</span><br><span style='font-size: 10pt; '>SO!GIS
Koordination</span><br><span style='font-size: 10pt; '>R&ouml;tistrasse
4</span><br><span style='font-size: 10pt; '>CH-4501 Solothurn</span></div>
<br>
<div class="Normal"><span style='font-size: 10pt; '>Telefon ++41(0)32 627 25
32</span><br><span style='font-size: 10pt; '>Telefax ++41(0)32 627 22
14</span></div>
<br>
<div class="Normal"><span style='font-size: 10pt; \
'>mailto:horst.duester@bd.so.ch</span><br><span style='font-size: 10pt; \
'>http://www.agi.so.ch</span></div> <br>

</body>

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["aline1.sql" (application/octet-stream)]
["aline2.sql" (application/octet-stream)]
["intersecterror.png" (application/octet-stream)]

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