<HTML dir=ltr><HEAD><TITLE>RE: [postgis-users] match line with road segment</TITLE>
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<DIV dir=ltr><FONT face=Arial color=#000000 size=2>Now you do your make line. But you'll have to take into consideration what Paolo Rizzi said afterward. Not sure the easiest way to do that.</FONT></DIV>
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<DIV dir=ltr><FONT face=Arial size=2>So basically your process should look something like the below where trip_id is some fied that uniquely identifies each trip. The below snaps each point to closest road segment and then makes a line for each trip. It assumes the pt.gid is in the order of time travel. If you have a datetime field for each point, use that instead of the pt.gid.</FONT></DIV>
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<DIV dir=ltr> SELECT trip_id, ST_MakeLine(snapped_point) As trip_route<PRE>(SELECT<BR>pt_id,<BR>ln_id,<BR><BR>ST_Line_Interpolate_Point(<BR> ln_geom,<BR> ST_Line_Locate_Point(ln_geom, pt_geom)<BR> ) As snapped_point,</PRE><PRE>travel_id<BR><BR>FROM<BR>(<BR>SELECT DISTINCT ON (pt.gid)<BR> ln.the_geom AS ln_geom,<BR> pt.the_geom AS pt_geom,<BR> ln.id AS ln_id,<BR> pt.gid AS pt_id,pt.trip_id<BR>FROM<BR>gps_points pt INNER JOIN<BR>road_table ln<BR>ON<BR>ST_DWithin(pt.the_geom, ln.the_geom, 10.0)<BR>ORDER BY<BR>pt.gid,ST_Distance(ln.the_geom, pt.the_geom)<BR>) AS subquery ORDER BY trip_id, pt_id) As snapped_points</PRE><PRE>GROUP BY travel_id;</PRE></DIV>
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<DIV dir=ltr><FONT face=Arial size=2>Hope that helps,</FONT></DIV>
<DIV dir=ltr><FONT face=Arial size=2>Regina</FONT></DIV></DIV>
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<FONT face=Tahoma size=2><B>From:</B> postgis-users-bounces@postgis.refractions.net on behalf of searchelite<BR><B>Sent:</B> Thu 7/17/2008 10:23 AM<BR><B>To:</B> postgis-users@postgis.refractions.net<BR><B>Subject:</B> RE: [postgis-users] match line with road segment<BR></FONT><BR></DIV>
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<P><FONT size=2>Paragon Corporation-2 wrote:<BR>><BR>> You may be better off snapping the points to the line first before you do<BR>> a<BR>> make line. Take a look at Paul's blog entry. <BR>><BR>><BR>> <A href="http://blog.cleverelephant.ca/2008/04/snapping-points-in-postgis.html">http://blog.cleverelephant.ca/2008/04/snapping-points-in-postgis.html</A><BR>><BR>> Sounds similar to what you are trying to do.<BR>><BR>> Hope that helps,<BR>> Regina<BR>><BR>><BR><BR>Thanks for the reply...Yes, I already did that (snapping the point to the<BR>line)..so, is there any idea what should i do next?<BR>thanks<BR>--<BR>View this message in context: <A href="http://www.nabble.com/match-line-with-road-segment-tp18479996p18509643.html">http://www.nabble.com/match-line-with-road-segment-tp18479996p18509643.html</A><BR>Sent from the PostGIS - User mailing list archive at Nabble.com.<BR><BR>_______________________________________________<BR>postgis-users mailing list<BR>postgis-users@postgis.refractions.net<BR><A href="http://postgis.refractions.net/mailman/listinfo/postgis-users">http://postgis.refractions.net/mailman/listinfo/postgis-users</A><BR></FONT></P></DIV></BODY></HTML>
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