[postgis-users] Get concave hull from an array of longitudeinlatitude points

[Obe, Regina]

Are scratch that thought.  That's not right either.
-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net on behalf of Obe, Regina
Sent: Mon 11/24/2008 2:16 PM
To: PostGIS Users Discussion
Subject: RE: [postgis-users] Get concave hull from an array of longitudeinlatitude points
 
Evidentally its this thing
http://ubicomp.algoritmi.uminho.pt/local/concavehull.html

So I guess basically you take the boundary and you get rid of points
that have points sitting to the right/left/top/or bottom of it and then
you form a polygon from the remaining points.

Well at least that is what it seems like to me visually.  Just not quite sure how to program such a thing without writing yuck procedural code.

Hope that helps,
Regina


-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net on behalf of Martin Davis
Sent: Mon 11/24/2008 1:58 PM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] Get concave hull from an array of longitude inlatitude points
 
What's a concave hull?

Ales Kecman wrote:
> Hi!
>
>
> I'm new to Postgis and would really like to get some help on getting a 
> concave hull from an array of points.
>
> For example:
>
> I have an array of points - longitude and latitude of buildings in 
> particular area in the city. I already managed to get a convex hull 
> polygon from this array of points, but this is not really helpful. 
> What I'm trying to get is some kind of concave hull polygon from an 
> array of points, which I would further like to use in Google Earth kml 
> file.
>
> Thanks.
> ------------------------------------------------------------------------
>
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-- 
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022

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