[postgis-users] Postgis 1.4 - Obtain closest point of point over polylines layer (without st_ClosestPoint)

[Aitor Gil Martin]

I´ve got a polylines layer (pipes) and a points layer (valves) and In Postgis 1.4 I would like to obtain the closest points but exactly on the closest polyline. In other words, i need to locate each valve over the closest point on a pipe but taking into account that there is not only one polyline but many and that i am using postgis 1.4 and St_ClosestPoint() that could help to solve this problem doesn't still exist on my postgis version.

 

I read that the following statement works if it is used for one polyline, but I need to be processed for all the polylines on the table:

SELECT ST_Line_Interpolate_Point(
               line_to_project_onto.the_geom,
               ST_Line_Locate_Point(
                       line_to_project_onto.the_geom,
                       points_to_project_onto_line.the_geom
               )
        )
FROM line_to_project_onto, points_to_project_onto_line;

If theres a way to add the St_ClosestPoint() function to my Postgis 1.4 could also help but i think i need to create a new function for this. Thanks in advance. 

Regards, 

 

Aitor Gil Martin

Departamento Informática

Getxoko Udala / Ayto Getxo

Tel: 94 466 02 16 Ext.- 3457

www.getxo.net <http://www.getxo.net/> 

agmartin <mailto:agmartin at getxo.net> @getxo.net <mailto:agmartin at getxo.net> 

 

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