[postgis-users] [Postgis-User] Different between geometry and geography?

[Peter Hopfgartner]

Hi Nguyen

In PostGIS context, a GEOMETRY is in a 2d plane, a GEOGRAPHY is basically on a sphere/geoid/ellipsoid, see http://postgis.refractions.net/documentation/manual-1.5/ch04.html#PostGIS_Geography

Peter

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--------nguyen liem <liemnguyendl at gmail.com> wrote--------
Subject: [postgis-users] [Postgis-User] Different between geometry and	geography?
Date: 09.07.2010 08:44

>Hi everyone,
>http://postgis.refractions.net/docs/ST_DWithin.html
>I see the ST_DWithin function that we can we can determine the geometries
>are within a specified distance of one another.
>*
>ST_DWithin*(*geometry* g1, *geometry *g2, double precision
>distance_of_srid)
>;
>*ST_DWithin*(*geography* gg1, *geography *gg2, double precision
>distance_meters);
>
>Could you explain me when we use *geometry *and when *geography*.
>    Geometry which is a geometry tupe: POINT, LINE, POLYGON ... ?
>    Geography: ...?
>    ...
>
>Cheers.
>
>-- 
>Liem Nguyen
>Developer
>Axon Active Corp.
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