'RE: [postgis-users] Get concave hull from an array of longitude'

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List: postgis-users
Subject: RE: [postgis-users] Get concave hull from an array of longitude
From: "Obe, Regina" <robe.dnd () cityofboston ! gov>
Date: 2008-11-24 19:16:29
Message-ID: 53F9CF533E1AA14EA1F8C5C08ABC08D204D7F03C () ZDND ! DND ! boston ! cob
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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@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.
> ------------------------------------------------------------------------
> 
> _______________________________________________
> postgis-users mailing list
> postgis-users@postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users
> 

-- 
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022

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<P><FONT SIZE=2>Evidentally its this thing<BR>
<A HREF="http://ubicomp.algoritmi.uminho.pt/local/concavehull.html">http://ubicomp.algoritmi.uminho.pt/local/concavehull.html</A><BR>
 <BR>
So I guess basically you take the boundary and you get rid of points<BR>
that have points sitting to the right/left/top/or bottom of it and then<BR>
you form a polygon from the remaining points.<BR>
<BR>
Well at least that is what it seems like to me visually.&nbsp; Just not quite sure \
how to program such a thing without writing yuck procedural code.<BR> <BR>
Hope that helps,<BR>
Regina<BR>
<BR>
<BR>
-----Original Message-----<BR>
From: postgis-users-bounces@postgis.refractions.net on behalf of Martin Davis<BR>
Sent: Mon 11/24/2008 1:58 PM<BR>
To: PostGIS Users Discussion<BR>
Subject: Re: [postgis-users] Get concave hull from an array of longitude inlatitude \
points<BR> <BR>
What's a concave hull?<BR>
<BR>
Ales Kecman wrote:<BR>
&gt; Hi!<BR>
&gt;<BR>
&gt;<BR>
&gt; I'm new to Postgis and would really like to get some help on getting a<BR>
&gt; concave hull from an array of points.<BR>
&gt;<BR>
&gt; For example:<BR>
&gt;<BR>
&gt; I have an array of points - longitude and latitude of buildings in<BR>
&gt; particular area in the city. I already managed to get a convex hull<BR>
&gt; polygon from this array of points, but this is not really helpful.<BR>
&gt; What I'm trying to get is some kind of concave hull polygon from an<BR>
&gt; array of points, which I would further like to use in Google Earth kml<BR>
&gt; file.<BR>
&gt;<BR>
&gt; Thanks.<BR>
&gt; ------------------------------------------------------------------------<BR>
&gt;<BR>
&gt; _______________________________________________<BR>
&gt; postgis-users mailing list<BR>
&gt; postgis-users@postgis.refractions.net<BR>
&gt; <A HREF="http://postgis.refractions.net/mailman/listinfo/postgis-users">http://postgis.refractions.net/mailman/listinfo/postgis-users</A><BR>
 &gt;&nbsp;&nbsp;<BR>
<BR>
--<BR>
Martin Davis<BR>
Senior Technical Architect<BR>
Refractions Research, Inc.<BR>
(250) 383-3022<BR>
<BR>
_______________________________________________<BR>
postgis-users mailing list<BR>
postgis-users@postgis.refractions.net<BR>
<A HREF="http://postgis.refractions.net/mailman/listinfo/postgis-users">http://postgis.refractions.net/mailman/listinfo/postgis-users</A><BR>
 <BR>
</FONT>
</P>

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