[R-sig-Geo] Distances in geoR package

[Tim Keitt]

For low-latitudes and small distances, the error should be
insignificant. You can check using proj.4 to compute some distances in
both Euclidean and geodesic distances. For large distances or high
latitudes, you can 1) project to a Cartesian coordinate system or 2)
compute geodesic distances. I think there is an "earth.distance"
somewhere in R.

THK


On Thu, 2005-06-16 at 15:58 +0200, giovanna jona lasinio wrote:
> Dear all, this may be a stupid question, but I wasn't able to find an
> answer in the FAQ and in the mail archive.
> I have a huge amount of  data, 644 sites for 30 different  times, which
> coordinates are expressed in decimal longitude and latitude, I'd like to
> simply compute the empirical variogram and use "variofit" to estimate
> variogram's parameters for each time. The "variog" function uses
> euclidean distances and then it is not appropriate for lon-lat
> coordinate. Is there any way to change the distance type in "variog"? Or
> which information are necessary to "variofit" in order to estimate
> variogram's parameters?
> 
> Thanks for any help
> Giovanna Jona Lasinio
> 
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-- 
Tim Keitt
Section of Integrative Biology
http://www.keittlab.org/