AI-GEOSTATS: Variogram estimation

[Arie Croitoru]

Dear list members,   Following Ruben Roa's email, I would like to add that I did not find any clear criterion to what is the minimum number of data pairs that should be used in each lag and this would certainly affect the variogram uncertainty. I know that a minimum of 30 data pairs is used frequently but my impression is that this is a "rule of thumb". I guess this rule originated from the central limit theorem (?). I found that the lack of a clear criterion might have a big effect on the estimation of the Variogram especially in cases where the data points are non regular and in cases where a non parametric variogram might be considered.   I would gratefully appreciate any comments on this as well.   Thanks,   Arie.