To: PostGIS Users Discussion
Subject: Re: [postgis-users] Distance between two furthest points of a group
Maybe you can even reduce this with cte :
with collected_geom AS (
select st_collect(geom) as geoms
from your_points
)
SELECT ST_LonguestLine(t1.geoms,t2.geoms)
FROM collected_geom AS t1
Maybe you can even reduce this with cte :
with collected_geom AS (
select st_collect(geom) as geoms
from your_points
)
SELECT ST_LonguestLine(t1.geoms,t2.geoms)
FROM collected_geom AS t1, collected_geom AS t2
Cheers,
Rémi-C
2015-06-30 8:48 GMT+02:00 Nick Ves vesni...@gmail.com:
Didn't know
Didn't know about st_LongestLine.
Just tried and it amazed me!
on a dataset of 220k points (on a projected crs) it took ~ 1.5 secs to
answer the querry :
select 1 as id, ST_LongestLine(st_collect(geom),st_collect(geom)) geom
from points ;
N
On Sat, Jun 27, 2015 at 2:41 PM, Nicklas Avén
Maybe I'm wrong, but your 2 farthest points should be on the boundary of
the maximum bounding circle (feels right but couldn't prove it).
Thus you would compute this circle, then filter points not too far from it,
then take the points with the max distance using an inner join (same as
Nick, but
Hallo
I haven't followed the whole conversation.
But one way is to collect alk points and usr ST_maxdistance on the colnections.
or st_longestline. longestline will return a line where the end points is the
two points furthest from eath other. Those functions is quite fast.
/Nicklas
Sent
Le 26/06/2015 13:54, Jonathan Moules a écrit :
I have sets of points (up to 250,000 in a set) and I want to get the
furthest distance between any of them.
In theory the simplest way is to use
ST_MinimumBoundingCircle(ST_Collect(geography) and then get the diameter
of that.
You can cross join to create the cartesian product of them and use it to
calculate the distance of each with regards to the other:
select a.id,b.id, st_distance(a.geom,b.geom) d from points a cross join
points b order by d desc limit 1;
ofc that will take forever because it will have to create
Hm,
I don't understand your problem.
The circle seems to be the perfect solution.
Do you mean the function returns nothing?
Maybe you could try to scale down you points(scaling down centered of
centroid of your points )?.
Cheers,
Rémi-C
2015-06-26 13:54 GMT+02:00 Jonathan Moules
Hi List,
I have sets of points (up to 250,000 in a set) and I want to get the furthest
distance between any of them.
In theory the simplest way is to use
ST_MinimumBoundingCircle(ST_Collect(geography) and then get the diameter of
that.
The problem is - I don't seem to be able to get the
