[postgis-users] st_dist, st_sphere, st_spheroid - overhead/efficiency question

[Bo Coughlin]

Tried - got nothing returned...little scary. - bo

Bo Coughlin
bo at rekindl.com
704.414.0805


On Thu, Jul 9, 2009 at 1:16 PM, Paul Ramsey <pramsey at cleverelephant.ca>wrote:

> Try this:
>
> --
> -- ST_DWithin_Sphere(lonlat-point, lonlat-point, radius-in-meters)
> returns boolean
> --
> -- Meters/Degree @ 60N: select 1/distance_sphere('POINT(0
> 60)','POINT(1 60)') = 1.79866403673916e-05
> --
> CREATE OR REPLACE FUNCTION ST_DWithin_Sphere(geometry, geometry, float8)
>        RETURNS boolean
>        AS 'SELECT $1 && ST_Expand($2,$3 * 1.79866403673916e-05) AND
> $2 && ST_Expand($1,$3 * 1.79866403673916e-05) AND
> ST_Distance_Sphere($1, $2) < $3'
>        LANGUAGE 'SQL' IMMUTABLE;
>
>
> SELECT m.id AS mid,
> m.building_i AS mb_id,
> c.id AS cid, c.building_i AS cb_id,
> m.streetaddr AS m_address,
> m.city AS m_city,
> m.state AS m_state,
> m.zip AS m_zip,
> m.zip4 AS m_zip4,
> round(CAST(
> ST_Distance_Sphere(m.the_geom, c.the_geom)
> AS numeric), 2) AS dist_meters
> FROM market_locations m, customer_locations c
> WHERE st_dwithin_sphere(m.the_geom, c.the_geom, 2414.016)
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>
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