Thank you very much.
________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Rodrigo Martín LÓPEZ GREGORIO Sent: Wednesday, August 15, 2007 5:44 PM To: PostGIS Users Discussion Subject: Re: [postgis-users] Extracting a line from multilinestring Hi Brian... I think you can do one of this things: 1. If you are sure that all your geometries have just one LINESTRING then you can do: 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 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: 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 If you want to verify if all your geometries have just one LINESTRING you can try: SELECT count(*) FROM roads WHERE NumGeometries(the_geom) > 1 This will return the number of MULTILINESTRINGS that have more than one LINESTRING Rodrigo On 8/15/07, Peck, Brian <[EMAIL PROTECTED]> wrote: Hey all, Does anyone if there is a way to extract a line from a MultiLineString? I am trying to make the call 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 But I get the error ERROR: line_locate_point: 1st arg isn't a line My 'the_geom' field is filed with MultiLineString data (though only LineString in each one). Ex: select AsText(the_geom) from roads limit 1; astext ------------------------------------------------------------------------------------------ MULTILINESTRING((-74.4595680236816 40.0301723480225,-74.4591522216797 40.0302429199219)) (1 row) - Brian Peck _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
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