Thanks very much for the help!


Scott
On Monday, April 11, 2011 at 12:54 PM, Seeliger.Curt@epamail.epa.gov wrote: 
> I have a bunch of geographic locations specified by lat-long 
> > coordinates. What's an easy way to calculate geographic distance 
> > between any two points? OR, perhaps there is a function for 
> > calculating a distance matrix for K sites? 
> 
> A comparison of some geographic distance calculations is provided at 
> http://pineda-krch.com/2010/11/23/great-circle-distance-calculations-in-r/ 
> , along with code for calculating the Vincenty inverse formula, which 
> relies on the WGS-84 ellipsoid approximations.
> 
> The author compares the results to fields::rdist.earth, which seems to 
> rely on a spherical model of the earth. It would be interesting to 
> compare it to other distance functions as well.
> 
> I found that the function provided at the above URL did not handle the 
> case of coincident points. Adding the following line after the while loop 
> fixed this.
>  if (iterLimit==100) return(0) # formula began with nearly or 
> exactly coincident points
> 
> Enjoy the days,
> cur
> -- 
> Curt Seeliger, Data Ranger
> Raytheon Information Services - Contractor to ORD
> seeliger.curt@epa.gov
> 541/754-4638
> 
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> 
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