boundaries for variogram

I noticed that autofitVariogram sets boundaries for the call to
gstat::variogram along the lines of (0.35 * diag(bbox(sp)) /100) *
c(2, 4, 6, 9, 12, 15, 25, 35, 50, 65, 80, 100).  Any idea of the basis
of this method?

Mark

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Hi Mark,

Those values are quite a pragmatic choice, as I (and my co-authors) 
write in my paper[1]:

Any of the assumptions made may leave room for improvement of the 
procedures. As a first start, and for the purpose of automated mapping 
of natural ambient dose rates, they seemed appropriate.

But I'm open to a discussion on improving, do you have any concrete 
ideas right now?

Paul
package maintainer of automap

[1] http://dx.doi.org/10.1016/j.cageo.2008.10.011

Drs. Paul Hiemstra
Department of Physical Geography
Faculty of Geosciences
University of Utrecht
Heidelberglaan 2
P.O. Box 80.115
3508 TC Utrecht
Phone:  +3130 253 5773
http://intamap.geo.uu.nl/~paul
http://nl.linkedin.com/pub/paul-hiemstra/20/30b/770