find nearest point on line where distance to point not on line is minimum - or lets say drop a perpendicular on the nearest line through a given point
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find nearest point on line where distance to point not on line is minimum - or lets say drop a perpendicular on the nearest line through a given point
by Marco Lechner - FOSSGIS e.V.
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hi,
I try to find a way to solve this problem in postgis. I have a table with lines an coorindates of a point that needn't to be on a line. I try to find 1. the id of the line wich is nearest to the point 2. get the coordinates of the point on the line which is nearest to the point --------0--------- | | X (point X not on line) 0 is the nearest Point to X on line and therefore the Point i'm searching for. Any hints? Marco -- FOSSGIS e.V. die unabhängige Hilfe bei freier GIS-Software und freien Geodaten www.fossgis.de +++++++++++++++++++++++++++++++++ _______________________________________________ postgis-users mailing list postgis-users@... http://postgis.refractions.net/mailman/listinfo/postgis-users |
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Re: find nearest point on line where distance to point not on line is minimum - or lets say drop a perpendicular on the nearest line through a given point
by Mehmet-7
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hi, i think you're searching this: bye
2009/10/16 Marco Lechner - FOSSGIS e.V. <marco.lechner@...> hi, _______________________________________________ postgis-users mailing list postgis-users@... http://postgis.refractions.net/mailman/listinfo/postgis-users |
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Re: find nearest point on line where distance to point not on line is minimum - or lets say drop a perpendicular on the nearest line through a given point
by Marco Lechner - FOSSGIS e.V.
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Hi Mehmet,
thank you. This seems to be much faster then my experiments combining line_locate_point() and line_interpolate_point() in subselects. The main problem is now, that i have a bunch of lines (not just one specific) in a table and I want the point to be calculated on the nearest line. The recent request takes about 1.2 seconds because I have to calculate the distances to all lines first to identify the nearest line. Is there a better way? Recent request: SELECT multiline_locate_point(line, point) AS Ppoint_on_line FROM (SELECT distance(the_geom, pointfromtext('POINT(3440580 5350000)', 31467)) AS dist, pointfromtext('POINT(3440580 5350000)', 31467) AS point, the_geom AS line FROM linetable ORDER BY dist LIMIT 1) as foo Marco Mehmet Sirin schrieb: > hi, i think you're searching this: > http://pgrouting.postlbs.org/wiki/LoadingtheCode4 > bye > > 2009/10/16 Marco Lechner - FOSSGIS e.V. <marco.lechner@... > <mailto:marco.lechner@...>> > > hi, > > I try to find a way to solve this problem in postgis. > I have a table with lines an coorindates of a point that needn't to be > on a line. I try to find > 1. the id of the line wich is nearest to the point > 2. get the coordinates of the point on the line which is nearest to the > point > > --------0--------- > | > | > X (point X not on line) > > 0 is the nearest Point to X on line and therefore the Point i'm > searching for. > > Any hints? > > Marco > > -- > > FOSSGIS e.V. > die unabhängige Hilfe bei freier GIS-Software und freien Geodaten > www.fossgis.de <http://www.fossgis.de> > > +++++++++++++++++++++++++++++++++ > _______________________________________________ > postgis-users mailing list > postgis-users@... > <mailto:postgis-users@...> > http://postgis.refractions.net/mailman/listinfo/postgis-users > > > > ------------------------------------------------------------------------ > > _______________________________________________ > postgis-users mailing list > postgis-users@... > http://postgis.refractions.net/mailman/listinfo/postgis-users -- ++++++++BITTE VORMERKEN++++++++ INTERGEO 2009: 22.09. - 24.09.2009 in Karlsruhe; Halle 1, Stand 1.417 +++++++++++++++++++++++++++++++ FOSSGIS e.V. die unabhängige Hilfe bei freier GIS-Software und freien Geodaten www.fossgis.de +++++++++++++++++++++++++++++++++ _______________________________________________ postgis-users mailing list postgis-users@... http://postgis.refractions.net/mailman/listinfo/postgis-users |
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Re: find nearest point on line where distance to point not on line is minimum - or lets say drop a perpendicular on the nearest line through a given point
by Paragon Corporation-2
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Marco,
I think what you want is something like this http://blog.cleverelephant.ca/2008/04/snapping-points-in-postgis.html The key is you want to use ST_DWithin and come up with a distance that is longer than any 2 closest lines. This will weed out a lot of falses with a spatial index so should be much faster than what you are doing. Hope that helps, Regina -----Original Message----- From: postgis-users-bounces@... [mailto:postgis-users-bounces@...] On Behalf Of Marco Lechner - FOSSGIS e.V. Sent: Friday, October 16, 2009 7:55 AM To: PostGIS Users Discussion Subject: Re: [postgis-users] find nearest point on line where distance to point not on line is minimum - or lets say drop a perpendicular on the nearest line through a given point Hi Mehmet, thank you. This seems to be much faster then my experiments combining line_locate_point() and line_interpolate_point() in subselects. The main problem is now, that i have a bunch of lines (not just one specific) in a table and I want the point to be calculated on the nearest line. The recent request takes about 1.2 seconds because I have to calculate the distances to all lines first to identify the nearest line. Is there a better way? Recent request: SELECT multiline_locate_point(line, point) AS Ppoint_on_line FROM (SELECT distance(the_geom, pointfromtext('POINT(3440580 5350000)', 31467)) AS dist, pointfromtext('POINT(3440580 5350000)', 31467) AS point, the_geom AS line FROM linetable ORDER BY dist LIMIT 1) as foo Marco Mehmet Sirin schrieb: > hi, i think you're searching this: > http://pgrouting.postlbs.org/wiki/LoadingtheCode4 > bye > > 2009/10/16 Marco Lechner - FOSSGIS e.V. <marco.lechner@... > <mailto:marco.lechner@...>> > > hi, > > I try to find a way to solve this problem in postgis. > I have a table with lines an coorindates of a point that needn't to be > on a line. I try to find > 1. the id of the line wich is nearest to the point > 2. get the coordinates of the point on the line which is nearest to > point > > --------0--------- > | > | > X (point X not on line) > > 0 is the nearest Point to X on line and therefore the Point i'm > searching for. > > Any hints? > > Marco > > -- > > FOSSGIS e.V. > die unabhängige Hilfe bei freier GIS-Software und freien Geodaten > www.fossgis.de <http://www.fossgis.de> > > +++++++++++++++++++++++++++++++++ > _______________________________________________ > postgis-users mailing list > postgis-users@... > <mailto:postgis-users@...> > http://postgis.refractions.net/mailman/listinfo/postgis-users > > > > ---------------------------------------------------------------------- > -- > > _______________________________________________ > postgis-users mailing list > postgis-users@... > http://postgis.refractions.net/mailman/listinfo/postgis-users -- ++++++++BITTE VORMERKEN++++++++ INTERGEO 2009: 22.09. - 24.09.2009 in Karlsruhe; Halle 1, Stand 1.417 +++++++++++++++++++++++++++++++ FOSSGIS e.V. die unabhängige Hilfe bei freier GIS-Software und freien Geodaten www.fossgis.de +++++++++++++++++++++++++++++++++ _______________________________________________ postgis-users mailing list postgis-users@... http://postgis.refractions.net/mailman/listinfo/postgis-users _______________________________________________ postgis-users mailing list postgis-users@... http://postgis.refractions.net/mailman/listinfo/postgis-users |
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