[postgis-users] Amoeba Hulls

[Bruce Rindahl]

The easy answer is if was done in ArcView 3.x then the methodology can be
duplicated in PostGIS.  All you would need to do is view the avenue code and
recreate with the functions available in PostGIS.  Looping and iterations
could be hard but not impossible.

The hard question is what is the status of the avenue code?  If it is
copyrighted then you are stuck without the permission of the owner.

Bruce Rindahl

 

  _____  

From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of William
Andersen
Sent: Wednesday, July 05, 2006 11:44 AM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] Amoeba Hulls

 

Paul, Steve,

Thanks for the quick replies, unfortunately it's pretty hard to tell from
those images if they match.

I've done some more digging and it turns out that these shapes were created
in Arcview 3.x. The notes I have say... 

> This approach selects a number of the outliers and joins the extreme
points using elliptical arcs. 
> The arcs are all created in a direction moving out from the store.

However, I dont see customer points at the discontinuities in the hulls, so
it appears that the "extreme points" are perhaps interpolated. 


Will

On 7/5/06, Paul Ramsey <pramsey at refractions.net> wrote:

William,

It doesn't look like this is a standard algorithm, but more likely a
particular empirical technique provided by the particular software you
were using.  So substituting some other technique might yield a 
different shape entirely... do any of the techniques mentioned here
<http://www.geospatial-online.com/geospatialsolutions/article/articleDetail.
jsp?id=1348 >
sound like what was done to your data?

Paul

William Andersen wrote:
>
> I'm fairly new to postgis, and working to automate a number of
> processes.
>
> We are trying to compute market area polygons that look like the 
> attached image. These were created by some older software.
>
>
> They are referred to as Amoeba Hulls, and they contain 80% of a
> store's customers. However I can't find any solid documentation that 
> would allow me to reproduce them.
>
> Does anyone have any ideas how these shapes are created or an
> alternate name that I might be able to google? Additionally, we may
> be in a position to finance the development of this feature. 
>
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