I believe she is referring to the OSSFIM method developed by Webster &
McBratney
Burgess, T.M., R. Webster, A.B. McBratney (1981) Optimal interpolation
and isarithmic mapping of soil properties. IV Sampling strategy. The
journal of soil science 32(4), 643-660.
McBratney, A.B., R. Webster (1981) The design of optimal sampling
schemes for local estimation and mapping of regionalized variables: 2
program and examples. Computers and Geosciences 7: 335-365.
which has been implemented a.o. in gstat.
in R:
> library(gstat)
> ?ossfim
"The idea is old, simple, but still of value. If you want to map a
variable with a given accuracy, you will have to sample it. Suppose the
variogram of the variable is known. Given a regular sampling scheme,
the kriging standard error decreases when either (i) the data spacing
is smaller, or (ii) predictions are made for larger blocks. This
function helps quantifying this relationship. Ossfim probably refers to
``optimal sampling scheme for isarithmic mapping'"
This computes the kriging variance across a regular grid.
HTH,
D. G. Rossiter
Department of Earth Systems Analysis
International Institute for Geo-Information Science and Earth
Observation (ITC)
Hengelosestraat 99
PO Box 6, 7500 AA Enschede, The Netherlands
Phone: +31-(0)53 4874 499
Fax: +31-(0)53 4874 336
mailto:[EMAIL PROTECTED], Internet: http://www.itc.nl/personal/rossiter
On 14 Aug2006, at 04:51, Gerald van den Boogaart wrote:
Dear Kerry Ritter,
The kriging variance is different for different interpolation
locations. Thus
you can not give just one such curve.
Best regards,
Gerald v.d. Boogaart
Am Freitag, 11. August 2006 00:15 schrieb Kerry Ritter:
Hi. I am looking for a simple way to compute the kriging variance as
a
function of distance between sampling sites for a given spherical and
exponential semivariogram. I know that these variances do not depend
on
the data values, but on location. Thus, it seems like this would be a
common enough task where one would use this curve for completing a
cost-efficiency analyzes with regard to sample spacing. I currently
use
Splus/R.
Thaniks,
Kerry
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