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Hi,<br>
According to SQL/MM and in PostGIS the intersection of two
linestrings can be:<br>
<br>
a Empty ST_Point (GeometryCollection Empty in PostGIS 1.5)<br>
a ST_Point<br>
a ST_LineString<br>
a ST_MultiPoint<br>
a ST_MultiLineString<br>
a ST_GeomCollection with ST_Point and ST_LineString.<br>
<br>
Cheers,<br>
Jose<br>
<br>
<br>
<br>
On 19/03/2012 20:25, <a class="moz-txt-link-abbreviated" href="mailto:pcreso@pcreso.com">pcreso@pcreso.com</a> wrote:
<blockquote
cite="mid:1332185149.39935.YahooMailClassic@web160703.mail.bf1.yahoo.com"
type="cite">
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<td style="font: inherit;" valign="top">Whenever the
intersection of two lines is a linestring.<br>
<br>
eg: <br>
select
astext(ST_intersection(ST_makeline(ST_Makepoint(0,0),
ST_Makepoint(1,1)),ST_Makeline(ST_Makepoint(0.5, 0.5),
ST_Makepoint(1.5,1.5))));<br>
astext <br>
-------------------------<br>
LINESTRING(0.5 0.5,1 1)<br>
(1 row)<br>
<br>
Brent<br>
<br>
--- On <b>Tue, 3/20/12, Bob Pawley <i><a class="moz-txt-link-rfc2396E" href="mailto:rjpawley@shaw.ca"><rjpawley@shaw.ca></a></i></b>
wrote:<br>
<blockquote style="border-left: 2px solid rgb(16, 16,
255); margin-left: 5px; padding-left: 5px;"><br>
From: Bob Pawley <a class="moz-txt-link-rfc2396E" href="mailto:rjpawley@shaw.ca"><rjpawley@shaw.ca></a><br>
Subject: [postgis-users] St_intersection<br>
To: <a class="moz-txt-link-abbreviated" href="mailto:postgis-users@postgis.refractions.net">postgis-users@postgis.refractions.net</a><br>
Date: Tuesday, March 20, 2012, 6:44 AM<br>
<br>
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<div style="FONT-FAMILY:'Arial
Narrow';COLOR:#00002b;FONT-SIZE:12pt;">
<div>Hi</div>
<div> </div>
<div>I am querying a geometry looking for
intersection point between a line and an other
geometry.</div>
<div> </div>
<div>The return is 2 points and 2 linestrings.
(when I use st_union a geometry collection
results)</div>
<div> </div>
<div>Can anyone tell me under what conditions
that a st_intersection would return a
linestring??</div>
<div> </div>
<div>insert into num_search (the_geom3)</div>
<div>select
st_intersection(Num_Search.the_geom1,
entities.wkb_geometry) </div>
<div>from entities, Num_Search</div>
<div>where Num_Search.seq = 'R'</div>
<div>and st_intersects(entities.wkb_geometry,
Num_Search.the_geom1) = True</div>
<div> </div>
<div>Bob</div>
</div>
</div>
</div>
</div>
<br>
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