Please don’t count of autocasting of geometry -> geography. This makes your code brittle as it may change in the future.
You should explicitly cast your geometry to geography like ST_DWithin(a.geom::geography, b.geom::geography, somedistance) Or ST_DWithin(geography(a.geom), geography(b.geom), somedistance) Also keep in mind if you have spatial indexes on geometry – the above function can’t use them . You’d need to add functional indexes for geography Something like CREATE INDEX ix_yourtable_geom_geog_gist USING gist(geography(geom)); From: postgis-users [mailto:[email protected]] On Behalf Of Shaozhong SHI Sent: Friday, May 15, 2020 8:35 AM To: PostGIS Users Discussion <[email protected]> Subject: Re: [postgis-users] Spatial linking or selection Hi, Friends, I am a little bit confused. If I use geometry as data type, do I put something like 5 metres and use_spheroid=false? Is that correct? Regards, Shao On Fri, 15 May 2020 at 13:00, Giuseppe Broccolo <[email protected] <mailto:[email protected]> > wrote: Hi Shao, Il giorno ven 15 mag 2020 alle ore 11:56 Shaozhong SHI <[email protected] <mailto:[email protected]> > ha scritto: Hi, Nicolas, Thanks. That is very interesting. I will test it. I could not find information on how distance is defined. 0.01 stands on what unit? https://postgis.net/docs/ST_DWithin.html Have a look to this statement in the doc you linked: """ For geometry: The distance is specified in units defined by the spatial reference system of the geometries. For this function to make sense, the source geometries must both be of the same coordinate projection, having the same SRID. For geography units are in meters and measurement is defaulted to use_spheroid=true, for faster check, use_spheroid=false to measure along sphere. """ Giuseppe. _______________________________________________ postgis-users mailing list [email protected] <mailto:[email protected]> https://lists.osgeo.org/mailman/listinfo/postgis-users
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