[postgis-users] Creating a circle geometry

[strk at refractions.net]

On Wed, Feb 16, 2005 at 11:24:05AM -0500, Richard_D_Levine at raytheon.com wrote:
> What about creating a polygon approximation of the circle using buffer()?

Good idea. That would work.
Basically createCircle wouldn't do any better than that,
circle is still approximated... and you can specify number
of segments per quadrant.

--strk;


> 
> http://postgis.refractions.net/pipermail/postgis-users/2004-October/005949.html
> 
> Rick
> 
> 
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> 
> 
> 
> On Wed, Feb 16, 2005 at 11:05:35AM -0500, Surridge, Christopher S wrote:
> > I have the cvs version of postgis working on Solaris 10 now (thanks strk)
> and I'm trying to figure out how to insert a circle geometry. I have data
> that consists of a center given as a latitude/longitude and a radius in
> meters. There is a createCircle method in GEOS, but I can't figure out how
> to use it through postgis. Even if I could, looking through the code for
> createCircle, I'm not sure it will give the desired results for a lat/long
> coordinate system. I would settle for a bounding box created using expand,
> but I have the same concerns about the coordinate system in this case. Is
> there an easy way to do this that I'm missing, or do I just have to suck it
> up and do the meters to degrees and spherical coordinates math myself?
> 
> There is no postgis interface to GEOS createCircle.
> If there was, or you settle to use bounding box,
> you could try creating the geom in a isometric
> projection and then transform it back to lat/long.
> Also, consider incrementing the number of vertexes
> when doing so, to get better curves at transform
> time - see segmentize().
> 
> --strk;
> 
> >
> > Thanks,
> >
> > --chris
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