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I have a point whose latitude and longitude (only) are known, and a table of nodes with their geom. I want to find the closest node in the table to the given point.

I think I can achieve this with pgr_findNearestNodeDwithin function, but i cannot find the exact syntax of the function and the parameters it takes.

Any pointers in this direction will be appreciated.

2 Answers 2

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To find the nearest point you only need a little bit PostGIS. With PostGIS 2.0 or higher you can use nearest neighbor KNN gist functionality.

I assume you have a table with all nodes ("vertices"):

SELECT * FROM vertices 
    ORDER BY the_geom <-> ST_GeometryFromText('POINT(lon lat)',4326) 
    LIMIT 1;
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find_nearest_node_within_distance, in matching.sql

SELECT * FROM ( SELECT find_nearest_node_within_distance( 'POINT(x y)', 0.5, 'test_2po_4pgr') as x ) AS foo

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  • is that function available for pgrouting version 2? Jul 31, 2013 at 14:40
  • It is in matchinq.sql which is part of pgrouting or postgis ( i do not remember exactly ).
    – Matus
    Jul 31, 2013 at 14:41
  • matching.sql is not included in pgRouting 2 anymore.
    – dkastl
    Jul 31, 2013 at 16:18

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