Try moving your query into a subquery and then taking the max distance. Also, you can probably drop the subquery you
put as a parameter to the generate_series call. Why are you converting the geometry to text, then back to a geometry again?
ie.
SELECT "cellID", max(dist)
FROM (
-- Your query here, but also select the cellID to group on
SELECT
cellID,
distance_spheroid(
geometry_centroid,
ST_PointN(
ExteriorRing(geometry_zone),
generate_series(1, ST_NPoints(geometry_zone))
),
'SPHEROID["WGS 84",6378137,298.257223563]'
) AS dist
FROM "208_1_26624_zones"
WHERE > "cellID"='1'
) AS foo
GROUP BY "cellID";
-- Kevin
My Pid wrote:
Hello again,
I found the generate_series function (yes i am a newbie!) and I can use
it in order to calculate the distance between
my centroid (geometry_centroid) and my polygon (geometry_zone) with the
following request
SELECT
(distance_spheroid(geometry_centroid,ST_AsText(ST_PointN(ExteriorRing(geometry_zone),
generate_series(1,(SELECT npoints(geometry_zone) FROM
"208_1_26624_zones" WHERE "cellID"='1')))), 'SPHEROID["WGS
84",6378137,298.257223563]')) as d FROM "208_1_26624_zones" WHERE
"cellID"='1';
Now I can't use the max function because of the following error:
"set-valued function called in context that cannot accept a set"
when I use
SELECT
max(distance_spheroid(geometry_centroid,ST_AsText(ST_PointN(ExteriorRing(geometry_zone),
generate_series(1,(SELECT npoints(geometry_zone) FROM
"208_1_26624_zones" WHERE "cellID"='1')))), 'SPHEROID["WGS
84",6378137,298.257223563]')) as d FROM "208_1_26624_zones" WHERE
"cellID"='1';
any idea ?
thanks!
Nick
2009/2/18 My Pid <[email protected] <mailto:[email protected]>>
Hello,
I would like to know how I could get the maximum distance between a
POINT and a POLYGON.
(the POINT i am talking about here is in fact the ST_Centroid of the
mentionned POLYGON)
I looked for a function that transform my POLYGON into several POINT
but without success.
I am working with longitude, latitude, altitude for POINT
It is really the max distance that I am looking for (not the minimum
distance.)
and "accuracy" is important to me.
thanks in advance for your help !
regards,
Nick
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