[postgis-users] OT: Algorithm Suggestion

[Bruce Rindahl]

Given your point data in PostGIS what if you buffer each point and then
union the results?  The amount to buffer could be scale dependent.

Just an idea
Bruce Rindahl

-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Abe
Gillespie
Sent: Thursday, March 08, 2007 1:30 PM
To: PostGIS Users Discussion
Subject: [postgis-users] OT: Algorithm Suggestion

Hey all,

This is definitely off topic so please ignore if you could care less.
I'm not really sure where to go for this advice so PostGIS gets my
abuse.  Sorry.

I'm looking for a GIS algorithm (or an idea of an implementation) that
clumps scattered, overlapping point data into simple clumps that do
not overlap.

For instance:
Say we have a point for every building and house in a city.  Initially
we start zoomed such that the city boundary is entirely in view.  At
this view I'd like to have single non-overlapping points that
represent clumps of buildings.  Now say a specific clump right
downtown gets my attention.  I want to zoom in there and get a closer
look.  As I zoom in the clumps break apart into new clumps.
Eventually I'll zoom in enough to where the clump points are just each
single building.

At the most extreme zoomed-out level you'd see one single clump point
representing every single building (imagine you're zoomed way WAY
out).  At the most extreme zoomed-in level you'd have each individual
building point.

The biggest requirement here is having no points overlapping at any
zoom level.  The exact placement of these clumps is not an issue
though it should be roughly the average x,y of all the points the
clump represents.

Is there any algorithm in the GIS space that solves this problem?  It
doesn't seem like a very unique problem, but I've never run across it.
 Perhaps even PostGIS can do this (though I'm really looking for a
general solution)?

Also, adding to the complexity is the fact that my point locations are
dynamic.  So I couldn't just set up a set of layers for set zoom
levels.  I.e. the algorithm would have to run every time the map is
rendered.

Thanks for your help / ideas!
-Abe
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