On Thu, Mar 29, 2012 at 9:45 AM, Ian Dees <[email protected]> wrote: > After loading Cook County TIGER road features and OSM linear features into > PostGIS, I ran a simple query to find how well the roads matched: > > SELECT a.name, b.fullname, ST_HausdorffDistance(a.geom, b.geom) as dist > FROM cook_tiger a, cook_osm b > WHERE (a.geom && b.geom) AND ST_HausdorffDistance(a.geom, b.geom) < > 0.0005 > LIMIT 50 > > This returned results that made sense (the names matched in all 50 results). > > I removed the LIMIT clause and let it run before going to work to see how > many of the TIGER records match existing OSM features. > > Next up is building a table of TIGER -> OSM matches and using that to find > TIGER rows that don't have a corresponding OSM feature. > > If anyone has any ideas for speeding this up I'd love to hear it. It took > well over a couple hours to run one county. There are a lot of counties in > the US.
Very cool! To speed this up perhaps try limiting the number of times ST_HausdorffDistance is executed. First only run it for ways which are "close", such as falling inside a buffer, or even faster inside a bounding box. For a trivial speedup generate a table with distances first, then use the WHERE clause. However I have no idea how to form such queries! -Josh _______________________________________________ Talk-us mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk-us
