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 -- Dott. Peter Hopfgartner R3 GIS Srl - GmbH Via Johann Kravogl-Str. 2 I-39012 Meran/Merano (BZ) Email: [email protected] Tel. : +39 0473 494949 Fax : +39 0473 069902 www : http://www.r3-gis.com XING : http://www.xing.com/go/invita/8917535 --------nguyen liem <[email protected]> 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. >---------------------------------------------------------------------------- >Direct Line : +84 38 948 4645 >Fax : +84 38 811 3489 >Mobile Phone : +84 168 994 8897 >Skype ID : liemnguyendl2204 >Email : [email protected] / [email protected] >Web Site : http://axonactive.vn >Address : 87 Thang Long Street,Gate 2 Ward 4, > Tan Binh District, HCM city, Vietnam. > > >_______________________________________________ >postgis-users mailing list >[email protected] >http://postgis.refractions.net/mailman/listinfo/postgis-users > _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
