Thanks. Regina Obe. I will test it.
Regards, Shao On Fri, 15 May 2020 at 13:44, Regina Obe <[email protected]> wrote: > 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]> > wrote: > > Hi Shao, > > > > Il giorno ven 15 mag 2020 alle ore 11:56 Shaozhong SHI < > [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] > https://lists.osgeo.org/mailman/listinfo/postgis-users > > _______________________________________________ > postgis-users mailing list > [email protected] > https://lists.osgeo.org/mailman/listinfo/postgis-users
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