hi, just a suggestion: you should try a check to identify the line segment that don't lies in the road.
ST_PointN(geometry,integer) you can iterate and create the line segments. then you can run a ST_Contains to check if your road segment matches route segment. you should save the information of the line segment after and before the ST_Contains fails. with that information you can find the vertice and them interpolate to create him. best regards, Luigi Castro Cardeles 2008/7/18 searchelite <[EMAIL PROTECTED]>: > > > searchelite wrote: > > > > > > > > Obe, Regina DND\MIS wrote: > >> > >> 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. > >> > >> 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. > >> > >> SELECT trip_id, ST_MakeLine(snapped_point) As trip_route > >> (SELECT > >> pt_id, > >> ln_id, > >> > >> ST_Line_Interpolate_Point( > >> ln_geom, > >> ST_Line_Locate_Point(ln_geom, pt_geom) > >> ) As snapped_point, > >> travel_id > >> > >> FROM > >> ( > >> SELECT DISTINCT ON (pt.gid) > >> ln.the_geom AS ln_geom, > >> pt.the_geom AS pt_geom, > >> ln.id AS ln_id, > >> pt.gid AS pt_id,pt.trip_id > >> FROM > >> gps_points pt INNER JOIN > >> road_table ln > >> ON > >> ST_DWithin(pt.the_geom, ln.the_geom, 10.0) > >> ORDER BY > >> pt.gid,ST_Distance(ln.the_geom, pt.the_geom) > >> ) AS subquery ORDER BY trip_id, pt_id) As snapped_points > >> GROUP BY travel_id; > >> > >> Hope that helps, > >> Regina > >> > >> > > > > > > thanks a lot for the reply...i'll try the code you give me first thing > > tomorrow...:-) > > > > > > basically, the code you gave me just create a line from snapped points > right? what about matching the route with the road? I want to make the > route > like the illustration below > > http://www.nabble.com/file/p18522213/untitled.jpg > > > thank you > > > > -- > View this message in context: > http://www.nabble.com/match-line-with-road-segment-tp18479996p18522213.html > Sent from the PostGIS - User mailing list archive at Nabble.com. > > _______________________________________________ > postgis-users mailing list > postgis-users@postgis.refractions.net > http://postgis.refractions.net/mailman/listinfo/postgis-users >
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