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Do you have non-spatial control data? i.e. have you
measured resistivity at single locations at a number of frequencies? This should
help show you whether the effect you are seeing on the spatial data set is due
to uncreased accuracy with longer frequency (as suggested by Colin Badenhorst,
which would show up as a decreasing variance with increasing frequency at a
single location) or due to an interaction between the act of measurement and the
value being measured (which would show up as a regression towards an underlying
constant, value dependent on the environment), or some other cause, to be
postulated based on the results from the contol experiments. But the control
experiments are crucial - not just in this case, where you can (a posteriori)
see a need for them, but in any experiment involving data possibly
dependent on more than one primary factor (in this case, spatial location of
observation and observation frequency).
Barrie Wells
----- Original Message -----
Sent: Sunday, September 04, 2005 2:01
PM
Subject: [ai-geostats] Nugget
effect...
Dear list members,
I have a querry regarding the presence of nugget effect. I have brought
to the notice of my seniors before that iam working on the variography of the
resistivity data.
I have been monitoring the resisivity variations at a fixed point from
past many months with a frequency of 7 days or sometimes 14 days. I have come
across the remarkable changes in the resitivity values. Simultaneously i have
been incorporating the variograms on the acquired values of resitivity. As the
time is passing by the nuggest effect is decreasing witht the changes in the
resistivity values. though it is not sure the resistivity increase or
sometimes it decrease also but nugget effect is showing a decline in the
value. Iam not able to interpret this change in the nugget effect. though it
is good but in the initial value the nugget effect comes to be 1500 and then
after 1 month the value reduces to 300.
It would be help to me if list suggest me some thing better for my
interpretation work.
thanks in advance to all of you who consider me seriously.
regards
Rajni
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