[postgis-users] Amoeba Hulls

[William Andersen]

It appears to be the same as this functionality in Business Analyst

http://www.esri.com/software/arcgis/extensions/businessanalyst/about/customer-market.html

I thought this was done using some older version of Arcview, but i'm not
very familiar with esri's offerings.

Will

On 7/5/06, Paul Ramsey <pramsey at refractions.net> wrote:
>
> This wouldn't be in vanilla arcview, was it in Network Analyst? The top
> 80% of points by drive distance might yield this shape.  Finding the
> points would be straightforward, and then the hull building would be the
> hand-waving part.
>
> P
>
> William Andersen wrote:
> > 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
> > <mailto: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
> >     <
> 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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> >
> >
> >
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