[postgis-users] "Summarizing" a collection of geometries

[Reid Priedhorsky]

Dear list,

I would like to compute a "summary" of a collection of geometries 
(points, linestrings, polygons, or any combination).

Here is the use case. I would like to summarize the geometry collection 
and present this summary visually so users working at a small scale can 
see, "ah, if I zoom in here, I can see more details about this geometry 
collection".

The simple solution would be to compute a convex hull or bounding box, 
but this fails if the members of the collection are far apart (users 
could zoom into the middle and see nothing). In this case the summary 
would need to be a multipolygon. But the trick is figuring out when to 
split summary polygons into multipolygons.

Has this been done? Do any of you have suggestions or references?

It is very preferable to do this entirely in the database rather than in 
external code. Embedded procedures are fine.

As you can see I am not entirely sure of my terminology, so any 
suggestions there would be welcome as well.

Many thanks,

Reid