[postgis-users] Spatial linking or selection

[Bo Victor Thomsen]

It is explained on the same web page you're referring to: 
https://postgis.net/docs/ST_DWithin.html

For geometry: the distance unit of the geometries's srid (Coordinate 
reference system) . The line and point geometry must have the same srid

for geography: meters.

Den 15-05-2020 kl. 12:50 skrev Shaozhong SHI:
> 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
>
> Regards,
>
> Shao
>
> On Fri, 15 May 2020 at 11:32, Nicolas Ribot <nicolas.ribot at gmail.com 
> <mailto:nicolas.ribot at gmail.com>> wrote:
>
>     Hi,
>
>     You can test for proximity between start and end points
>     Create spatial indexes on st_startpoint(geom) and
>     st_endpoint(geom) on your line features table (also index starting
>     and ending points column in table one)
>
>     select t.id <http://t.id>, r.id <http://r.id>, r.geom
>     from start_end_table t join roads r on st_dwithin(t.startpoint,
>     st_startpoint(r.geom), 0.01) and st_dwithin(t.endpoint,
>     st_endpoint(r.geom), 0.01)
>
>     Adjust the 0.01 distance according to your data and their precision.
>
>     Nicolas
>
>     On Fri, 15 May 2020 at 11:42, Shaozhong SHI
>     <shishaozhong at gmail.com <mailto:shishaozhong at gmail.com>> wrote:
>
>         Given 2 tables.  One has the starting and ending points of
>         roads, and the other has line features.  How best to do
>         spatial linking or selection of road features?
>
>         Can anyone enlighten me?
>
>         Regards,
>
>         Shao
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-- 
Med venlig hilsen / Kind regards

Bo Victor Thomsen

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