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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Thank you very much.<o:p></o:p></span></font></p>
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10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'> postgis-users-bounces@postgis.refractions.net
[mailto:postgis-users-bounces@postgis.refractions.net] <b><span
style='font-weight:bold'>On Behalf Of </span></b>Rodrigo Martín LÓPEZ GREGORIO<br>
<b><span style='font-weight:bold'>Sent:</span></b> Wednesday, August 15, 2007
5:44 PM<br>
<b><span style='font-weight:bold'>To:</span></b> PostGIS Users Discussion<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [postgis-users]
Extracting a line from multilinestring</span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Hi Brian...<br>
<br>
I think you can do one of this things:<br>
<br>
1. If you are sure that all your geometries have just one LINESTRING then you
can do:<o:p></o:p></span></font></p>
<div style='margin-left:30.0pt'>
<p class=MsoNormal><i><font size=3 face="Times New Roman"><span
style='font-size:12.0pt;font-style:italic'>SELECT
line_interpolate_point(GeometryN(the_geom,1),line_locate_point(GeometryN(the_geom,1),PointFromText('POINT(-74.5
40)'))) FROM roads ORDER BY Distance(the_geom,PointFromText('POINT(-74.5 40)'))
LIMIT 1 </span></font></i><o:p></o:p></p>
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<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'><br>
2. If your geometries have more than one LINESTRING but this LINESTRINGS are
continuous (i.e. there are no gaps between the LINESTRINGS in a
MULTILINESTRING) you can use:<o:p></o:p></span></font></p>
<div style='margin-left:30.0pt'>
<p class=MsoNormal><i><font size=3 face="Times New Roman"><span
style='font-size:12.0pt;font-style:italic'>SELECT
line_interpolate_point(LineMerge(the_geom),line_locate_point(LineMerge(the_geom),PointFromText('POINT(-74.5
40)'))) FROM roads ORDER BY Distance(the_geom,PointFromText('POINT(- 74.5
40)')) LIMIT 1</span></font></i><o:p></o:p></p>
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<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'><br>
If you want to verify if all your geometries have just one LINESTRING you can
try:<o:p></o:p></span></font></p>
<div style='margin-left:30.0pt'>
<p class=MsoNormal><i><font size=3 face="Times New Roman"><span
style='font-size:12.0pt;font-style:italic'>SELECT count(*) FROM roads WHERE <span
class=term>NumGeometries(the_geom) > 1</span></span></font></i><o:p></o:p></p>
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<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'><br>
<span class=term>This will return the number of MULTILINESTRINGS that have more
than one LINESTRING </span><br>
<br>
<span class=term>Rodrigo</span><br>
<br>
<o:p></o:p></span></font></p>
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<p class=MsoNormal><span class=gmailquote><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>On 8/15/07, <b><span style='font-weight:bold'>Peck,
Brian</span></b> <<a href="mailto:brian.peck@lmco.com">brian.peck@lmco.com</a>>
wrote:</span></font></span><o:p></o:p></p>
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<div>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>Hey
all,</span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> </span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>Does
anyone if there is a way to extract a line from a MultiLineString?</span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> </span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>I
am trying to make the call</span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> </span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>SELECT
line_interpolate_point(the_geom,line_locate_point(the_geom,PointFromText('POINT(-74.5
40)'))) FROM roads ORDER BY Distance(the_geom,PointFromText('POINT(-74.5 40)'))
LIMIT 1</span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> </span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>But
I get the error</span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> </span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>ERROR:
line_locate_point: 1<sup>st</sup> arg isn't a line</span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> </span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>My
'the_geom' field is filed with MultiLineString data (though only LineString in
each one).</span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> </span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>Ex:
</span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> </span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>select
AsText(the_geom) from roads limit 1;</span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> </span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>
astext</span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>------------------------------------------------------------------------------------------</span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> MULTILINESTRING((-74.4595680236816
40.0301723480225,-74.4591522216797 40.0302429199219))</span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>(1
row)</span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> </span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>-
Brian Peck</span></font><o:p></o:p></p>
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