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

[Bo Coughlin]

sorry, need to be much more specific.
I have two tables of of original "raw"
data (prior to st_geomfrom text function)  - these lat/lon coordinates were
simple csv without projection.  created the geom via st function, wondering
if I may have used st_transform in one iteration as there was not projection
for the original data.

On Thu, Jul 9, 2009 at 1:54 PM, Paul Ramsey <pramsey at cleverelephant.ca>wrote:

> 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)
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> >>>
> >>
> >
> >
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