[geos-devel] Minimum Bounding Circle

[Obe, Regina]

I'm probably not the best person to answer this but based on my understanding.

I think you - 
1) Expose it in GEOS --  capi/geos_c.cpp, .h
2) Then on the PostGIS side create a function in lwgeom/lwgeom_geos.* that
calls the CAPI function.

Hope that helps,
Regina
-----Original Message-----
From: geos-devel-bounces at lists.osgeo.org on behalf of Bruce Rindahl
Sent: Tue 1/13/2009 1:21 PM
To: rindahl at lrcwe.com; GEOS Development List
Cc: Lee Meilleur
Subject: Re: [geos-devel] Minimum Bounding Circle
 
I am interested in exploring this issue further.  I believe the the 
computation of a minimum bounding circle is a requirement in evaluating 
congressional districts (Lee- Reference??).  If so then to have this 
function available to a program like PostGIS would be a plus.  I would 
like to test this module but need some help.  How do I  expose the 
module so it is available in PostGIS?

Bruce

Bruce Rindahl wrote:
> I just looked at MinimumDiameter.cpp and the code does the same thing 
> as the first part of my code linked by Regina.  This would be nice to 
> have except for one thing - it may not work.  It calls 
> distancePerpendicular which I couldn't find.  If this finds the point 
> furthest from the /extended/ line segment and uses this to compute the 
> diameter it is the same method as I used - rotate the geometry so the 
> segment is horizontal and compute the bounding box.  I can provide you 
> with a geometry where this algorithm fails.  Lee Meilleur can also 
> provide a counter example.  Because of this I changed my code to test 
> every point pair for the Minimum Diameter.
> Bruce Rindahl
>
> Martin Davis wrote:
>> Yes, this is computing the same thing as the Minimum Bounding Circle 
>> algorithm.  This algorithm appeared in JTS for some reason which is 
>> lost in the mists of time.  AFAIK it's never really been used or 
>> tested extensively.
>> It probably postdated the initial port of GEOS, and I guess nobody 
>> went looking for it until now...
>>
>> Obe, Regina wrote:
>>>
>>> I was snooping around the GEOS library and noticed a curious 
>>> algorithm class
>>> called MinimumDiameter.  As far as I can tell from scanning the code,
>>> it seems similar in concept to the the Minimum Bounding Circle 
>>> plpgsql algorithm that
>>> Bruce posted in November
>>>
>>> http://postgis.refractions.net/pipermail/postgis-users/2008-October/021734.html 
>>>
>>>
>>> Just wondering why this is not exposed in the CAPI interface or does 
>>> it server an entirely different purpose from what I am thinking.
>>>
>>> Thanks,
>>> Regina
>>>
>>>
>>>
>>>
>>>
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