# [postgis-users] Re: maximum distance between a POINT and POLYGON

nicklas.aven at jordogskog.no nicklas.aven at jordogskog.no
Thu Feb 19 05:49:35 PST 2009

```Hallo

What is the problem withST_Max_Distance(geometry g1, geometry g2)?

/Nicklas

2009-02-19 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 <mamat750 at gmail.com>
>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.
>
>
>regards,
>Nick
>
>
>
>
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