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Cost of nearest neighbor search depending on distance

Posted by smathermather on April 24, 2010

A quick review of costs to search with increasing distances. Reference this original post for the code being run.

SELECT DISTINCT ON(g1.gid)  g1.gid as gid, g2.gid as gid_ground, g1.x as x, g1.y as y, g2.z as z, g1.z - g2.z as height, g1.the_geom as geometry
 FROM veg As g1, ground As g2   
 WHERE g1.gid <> g2.gid AND ST_DWithin(g1.the_geom, g2.the_geom, 3.5)   
 ORDER BY g1.gid, ST_Distance(g1.the_geom,g2.the_geom);
This is the total query time comparing 167,000 to 222,000 points using ST_DWithin to do a nearest neighbor search with different search distances.

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This entry was posted on April 24, 2010 at 10:25 am and is filed under Database, PostGIS, SQL. Tagged: Database, Database Optimization, Digital Surface Model, FOSS, LiDAR, PostGIS. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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Cost of nearest neighbor search depending on distance

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