One must be a little careful, kriging is not a unique
interpolation method hence to say that one is going to
compare "kriging" with "IWD" does not make sense
First of all, is the mean treated as constant or a polynomial
(if the latter what terms are included, i.e., universal
kriging). Even if the mean is considered constant is it
considered known or unknown (simple vs ordinary kriging).
What variogram/covariance model(s) are used, what parameters
(including possible anisotropies). Is a unique neighborhood
used or a moving neighborhood, if the latter what conditions
are placed on it (radii, minimum/maximum number of points,
sectors, # of empty sectors?).
Note that the thin plate spline is a special case, i.e.,
a particular covariance.
Even IWD can vary, see Kane et al (Computers and Geosciences
1982) on an empirical study of the effect of the exponent.
To construct the contour map one must first interpolate onto
a regular grid, the choice of the grid mesh for interpolation
will have some effect.
Are point values interpolated or block values (one might
use either for contouring)?
What is the ultimate use of the contouring? That will have
some bearing on how to judge the comparison.
Finally the comparison will be valid only for the specific
data set and does in general not imply anything about
the comparison for a different data set.
Wanting to compare different possible results is an
interesting/useful question but it will not have a
Donald E. Meyrs
Donald E. Myers
Department of Mathematics
University of Arizona
Tucson, AZ 85721
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