[postgis-users] Re: Bounding Circle instead of Bounding Box

[Shane Spencer]

I figured it out a bit ago.. finally.. because I'm a dweeb..

I assumed buffer was a memory function :)  It greatly confused me.  I just
started up with PostGIS a few weeks ago and am just now seeing the term
buffer in all the programs I've been using for GIS visualization.

Thanks for the description :)

Shane

On 9/18/07, Nico Mandery <nicomandery at googlemail.com> wrote:
>
> Hi Shane,
>
> sorry for the delay, i had no access to the Internet for while.
>
> here is a short definition of the term buffer from
> http://www.fws.gov/data/IMADS/glossary.htm :
>
> buffer - A zone of a specified distance around coverage features. Both
> constant- and variable-width buffers can be generated for a set of
> coverage features based on each feature's attribute values. The
> resulting buffer zones form polygons-areas that are either inside or
> outside the specified buffer distance from each feature. Buffers are
> useful for proximity analysis (e.g., find all stream segments within
> 300 feet of a proposed logging area).
>
> In this context you could create a buffer with a distance X and a
> buffer with a distance Y around the point, and then look for point
> wicht are in the in the area of (bufferX-bufferY).
>
> nico
>
> >Could you reply with a URL to what buffers are and how they would be
> >used in this context? I'm >totally unfamiliar.
> >
> >
> > On 9/9/07, Nico Mandery < nicomandery <at> googlemail.com> wrote:
> >> Hi Rainer,
> >>
> >> You could could use a buffer instead of bounding boxes.
> >> Just an idea
> >>
> >> Nico
> >>
> >> Am Sonntag 09 September 2007 schrieb postgis <at> jochem.name:
> >> > Hi,
> >> >
> >> > what I want to do is finding certain features in some distance around
> a
> >> > certain point. Those features should be located in some corridor
> between X
> >> > and Y km around this point. Currently I've solved this problem by
> >> > computing two bounding boxes of X and Y km around the point and
> taking the
> >> > difference of those. So far so good.
> >> >
> >> > But I don't want to have some quadratic box but a real circle - is
> there
> >> > any way to achieve this?
> >> >
> >> > Best regards,
> >> > Rainer
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