[postgis-users] N-Point Buffer

[Stefano B.]

thanks

but the function azimuth is only on cvs 1.1 version?
and where is the online documentation?
It seems that the documentation link is wrong (on postgis site). If I try to
get the online documentation the link give me the pdf documentation file (I
think this file is older that the online docs).

I ask this questions because I don't know how to use the azimuth function. I
see on the web something like
azimuth(Geometry,Geometry)

You said me:

> 2) Order points by azimuth from [C] (Azimuth)

but I don't undestand how to use the azimuth function in order to to this.
(perhaps have I to insert the points in the first parameter and the centroid
in the second one?)

Very thanks for your help!
Stefano


----- Original Message ----- 
From: <strk at refractions.net>
To: "PostGIS Users Discussion" <postgis-users at postgis.refractions.net>
Sent: Wednesday, December 21, 2005 9:47 AM
Subject: Re: [postgis-users] N-Point Buffer


> On Wed, Dec 21, 2005 at 09:37:59AM +0100, Stefano B. wrote:
> > Hi,
> >
> > I have different set of points on my map. I'd like to create a buffer
(poligon) for each set (in order to display different "background areas" for
each set).
> >
> > So, how can I create a "buffer area" for a set of points?
> > The first idea:
> >
> >     - find the poligon that contains this points (1)
> >     - create a buffer of this poligon (2)
> >
> > (1) it seems, to me,  difficult (or not?)
> > (2) ...
> >
> > if is it the right way to do this, how can I find the polygon?
> > if it is the wrong way, what is the best method to to this?
>
> This is just an idea:
>
> 1) Build a multipoint and find it's centroid [C] (Collect, Centroid)
> 2) Order points by azimuth from [C] (Azimuth)
> 3) Build a line using ordered points (MakeLine)
> 4) Close the line (AddPoint, PointN)
> 5) Build a polygon (MakePolygon)
> 6) Buffer
>
> Sounds like possible with a single query ...
>
> --strk;
>
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