[postgis-users] min distance between two lines

[Stephen Woodbridge]

This might do what you want:

select st_distance_spheroid(a.the_geom, b.the_geom, 'SPHEROID["WGS 
84",6378137,298.257223563]') as minimum,
        st_distance_spheroid(st_centroid(a.the_geom), 
st_centroid(b.the_geom), 'SPHEROID["WGS 84",6378137,298.257223563]') as 
centroid
   from lines a, lines b
  where a.gid=<gid_a> and b.gid=<gid_b>

-Steve

On 11/20/2011 4:47 PM, muhammad imran wrote:
> Hi Gaurav,
>
> In principle, st_distance(geom, geom) always returns minimum distance
> between two geoms and it should work for any geom type (line,
> polygon, point). Function st_distance(st_centroid(geom),
> st_centroid(geom)) may return the distance between centroids of
> geoms. Calculating minimum distance of a geom to more than one geoms
> is however tricky a bit. It has been quite a long time, I developed a
> simple function (below) to find two nearest markets (among several
> markets) to a village location based on minimum (Euclidian) distance.
> You may have a look into it to get some idea. To find the centriod on
> minimum distance between two lines, you need to return a line
> geomtery, whereas st_distance_spheroid(geometry, geometry, spheroid)
> returns distance as double precision. You need to use a function that
> returns a shortest line between two gemoetries and then you can find
> centroid on the shortest line e.g.
> st_centroid(st_shortestline(geometry, geometry))
>
> Regards, Muhammad Imran PhD Student ITC, University of Twente
>
> CREATE OR REPLACE FUNCTION "Burkina_Faso"."BF_NN_MARKET_CAL"()
> RETURNS boolean AS' DECLARE i integer; result text;
>
> BEGIN FOR i in (select gid from "Burkina_Faso"."BF_VILLAGE_TAGED")
> loop insert into "Burkina_Faso"."BF_NN_MARKET" select b.gid,
> b.village,a.gid, a.market, min(st_distance(a.the_geom,
> b.the_geom))/1000 from "Burkina_Faso"."BF_MARKET" a,
> "Burkina_Faso"."BF_VILLAGE_TAGED" b where b.gid=i group by a.market,
> b.village, a.gid, b.gid, st_distance(a.the_geom, b.the_geom) having
> st_distance(a.the_geom, b.the_geom)=(select
> min(st_distance(a.the_geom, b.the_geom))) order by
> st_distance(a.the_geom, b.the_geom) asc limit 2; end loop; return
> true; END; ' LANGUAGE plpgsql;
>
> --- On Fri, 11/18/11, Gaurav Singh<singh09721 at itc.nl>  wrote:
>
>> From: Gaurav Singh<singh09721 at itc.nl> Subject: [postgis-users] min
>> distance between two lines To:
>> "postgis-users at postgis.refractions.net"<postgis-users at postgis.refractions.net>
>>
>>
Date: Friday, November 18, 2011, 3:33 PM
>> Hi All,
>>
>> I have two lines and I want to calculate the minimum distance
>> between them and finding the centroid between those two lines. Can
>> you help me telling of ST_Distance_Spheroid is the right method to
>> calculate the minimum distance between the two lines.
>>
>> Thanks, Gaurav Singh
>> _______________________________________________ postgis-users
>> mailing list postgis-users at postgis.refractions.net
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