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

[Bo Coughlin]

Hmmm....I just looked again at the points - they no longer match the
original lat/lon coordinates, could I have somehow altered these via
reprojecting them?
Bo Coughlin
bo at rekindl.com
704.414.0805


On Thu, Jul 9, 2009 at 1:38 PM, Bo Coughlin <bo at rekindl.com> wrote:

> 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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