[postgis-users] Convex Hull with a certain "offset"

[Stefano Bonnin]

Hi all,

I'm be able to create a convex hull of a certain number of points, but 
I'd like to find a convex hull "a little bit bigger". Is there a way to 
add a certain offset to the polygon
obtained from the convex hull query (like ST_expand for bounding boxes)

My query is:

select ST_ConvexHull(env) as poly From (SELECT ST_MakeLine(the_geom) as 
env from my_spatial_table Where gid  IN ( ... )) as foo


In other words I want to create a query like:

select ST_ConvexHull(env,50) as poly ....

where 50 is a value that increments the polygon dimensions in all 
directions.

Thanks in advance.
Stefano Bonnin

Comai Torino Srl
www.comai.to