Geometry Boost List: [ggl] nearest neighbor/segment

Subject: [ggl] nearest neighbor/segment
From: Matt Anderson (matt)
Date: 2011-08-16 22:06:07

   Hi Barend,

   Any news on the "nearest neighbor" function?  (see below)

   Or alternatively is there a way to get this information from the 
intersect algorithm? (which I have to run anyways...)

   thanks,

   Matt

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http://relativity.phys.lsu.edu/~matt/

On Fri, 10 Sep 2010, Barend Gehrels wrote:

> hi Matt,
>
> Welcome to the list.
>
>> 
>>   When a point is found to be within a polygon, is there a GGL method 
>> already in place to find the polygon segment and corresponding anchor nodes 
>> closest to that point within the polygon?
>> 
>> [...]  Does a method similar to above illustrated 'unkown_method' exist 
>> which would return the nodes in question?
>> 
>> 
>
> I once created a "nearest_neighbor" function which calculates exactly this 
> point. Because it was in draft and not completely finished, I didn't add it 
> yet. For this function it is not important if it lies inside or outside, and 
> can be used for a linestring, or even multi-point, as well.
> I was not sure about the name, and I believe in PostGIS it is called 
> ST_ClosestPoint, which is better. But (AFAIK) in PostGIS it will return zero 
> for a point within a polygon, so it is not completely similar. So if anyone 
> has a suggestion for the best name, it is welcome.
>
> I'll try to add it next weekend to the sandbox.
>
> Regards, Barend
>
>
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