[postgis-users] GEOMETRIES with different SRIDs

[Grant Edwards]

Thank you Paul, this is most useful




________________________________
From: Paul Ramsey <pramsey at cleverelephant.ca>
To: PostGIS Users Discussion <postgis-users at postgis.refractions.net>
Sent: Sunday, June 14, 2009 8:49:36 PM
Subject: Re: [postgis-users] GEOMETRIES with different SRIDs

Just skip the projections altogether.

select st_distance_sphere(st_makepoint(28.060455,
-26.056947),st_makepoint(18.3793284, -33.9228922))

This falls apart for queries with large tables, etc, because there's
no _sphere equivalent of st_dwithin that can leverage an index well.

P.

On Sun, Jun 14, 2009 at 9:20 AM, africa4you<a4uofbiz at yahoo.com> wrote:
>
> Hi
>
> I have two points in different SRID's and would like to calculate the
> distance between them, unfortunately this type of operation doesnt seem to
> be valid (Operation on two GEOMETRIES with different SRIDs ). Any help in
> solving this issue would be appreciated. Please see the sql below:
>
> Kind regards
>
> Grant Edwards
>
> SELECT postgis_full_version()
> "POSTGIS="1.3.3" GEOS="3.0.0-CAPI-1.4.1" PROJ="Rel. 4.6.0, 21 Dec 2007"
> USE_STATS"
>
>
>
> SELECT utmzone(ST_Centroid(setsrid((makepoint(28.060455,
> -26.056947)),4326))); //Johannesburg (utmzone = 32735)
> EPSG Projection 32735 - WGS 84 / UTM zone 35S
> http://spatialreference.org/ref/epsg/32735/
>
> SELECT utmzone(ST_Centroid(setsrid((makepoint(18.3793284,
> -33.9228922)),4326))); //Cape Town (utmzone = 32734)
> EPSG Projection 32734 - WGS 84 / UTM zone 34S
> http://spatialreference.org/ref/epsg/32734/
>
> SELECT  ST_Distance(ST_Transform(setsrid((makepoint(28.060455,
> -26.056947)),4326),utmzone(ST_Centroid(setsrid((makepoint(28.060455,
> -26.056947)),4326)))) ,
>                    ST_Transform(setsrid((makepoint(18.3793284,
> -33.9228922)),4326),utmzone(ST_Centroid(setsrid((makepoint(18.3793284,
> -33.9228922)),4326)))))  as dist_meters
>
>
> ERROR:  Operation on two GEOMETRIES with different SRIDs
> --
> View this message in context: http://www.nabble.com/GEOMETRIES-with-different-SRIDs-tp24022339p24022339.html
> Sent from the PostGIS - User mailing list archive at Nabble.com.
>
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