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

[Paul Ramsey]

Bo,

When you say something like "no longer match", knowing what you
started with and what you have now is useful to making any comment.

And there was no reprojection. ST_Transform() doesn't change the
on-disk values, it reprojects them on the fly. And you were, in any
event, asking for an identity transform, from 4326 to 4326.

P.

On Thu, Jul 9, 2009 at 10:46 AM, Bo Coughlin<bo at rekindl.com> wrote:
> 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)
>>> _______________________________________________
>>> postgis-users mailing list
>>> postgis-users at postgis.refractions.net
>>> http://postgis.refractions.net/mailman/listinfo/postgis-users
>>>
>>
>
>
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