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## AI-GEOSTATS: 3D-kriging with soil data

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• Dear all, how should soil data (~3300 profiles, ~150m average horizontal distance, all about 1 meter deep with different thickness of horizons representing
Message 1 of 3 , Jun 7, 2001
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Dear all,

how should soil data (~3300 profiles, ~150m average horizontal distance,
all about 1 meter deep with different thickness of horizons representing
type of soil, humus contents, ...) be kriged?

I need all information of the different horizons to calculate the somewhat
like ground water infiltration rate.

Does it make sense to use 3D-kriging methods? I think then there should a
modification of the z-coordinate be made. I mean stretching of the
z-coordinate. Does anyone know how to deal with the problem or some useful
textbook?

Or would you prefer to do 2D-kriging for a number of depths (10cm,
20cm,...), so there's no need to modify the z-coordinate?

Regards,
Markus

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• ... I would compute a vertical or downhole variogram to see if there if any significant spatial correlation in that direction. If so, you should attempt to
Message 2 of 3 , Jun 7, 2001
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At 01:03 PM 6/7/01 +0200, Markus Boehm wrote:
>Dear all,
>
>how should soil data (~3300 profiles, ~150m average horizontal distance,
>all about 1 meter deep with different thickness of horizons representing
>type of soil, humus contents, ...) be kriged?
>
>I need all information of the different horizons to calculate the somewhat
>like ground water infiltration rate.
>
>Does it make sense to use 3D-kriging methods? I think then there should a
>modification of the z-coordinate be made. I mean stretching of the
>z-coordinate. Does anyone know how to deal with the problem or some useful
>textbook?
>
>Or would you prefer to do 2D-kriging for a number of depths (10cm,
>20cm,...), so there's no need to modify the z-coordinate?
>
>
>Regards,
>Markus

I would compute a vertical or "downhole" variogram to see if there if any
significant spatial correlation in that direction. If so, you should
attempt to use a 3D kriging method, as it would be wasteful not to use that
information. You will have to use a very high value for anisotropy in the
Z direction (on the order of 1000 probably) or else leave the depth units
as cm and the horizontal units in m.

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• Dear List, sorry that you had to wait for this summary. I post the answers that I received in this Mail with the corresponding names and email addresses. The
Message 3 of 3 , Jun 21, 2001
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Dear List,

sorry that you had to wait for this summary.

I post the answers that I received in this Mail with the corresponding
names and email addresses. The answers were help for us to decide to do
kriging in 2-dimensional layers. However, so far do not have final results
but it seems to work fine this way.
Thanks to

Rudi Dutter <R.Dutter@...>:
(...
I was involved in a geochemical analysis project at the peninsula Kola
where we
had less data than you have, and also a much smaller amount of values in
the
z-direction. Nevertheless the results are documented in
C. Reiman et al. (1998): Environmental Geochemical Atlas of the Central
Barents
Region. Norges geologiske undersokelse (NGU), Geological Survey of Norway.

We experienced with kriging in 2-dimensional layers, and the results are
published. Only afterwards we started investigating the relations between
the
empirical structures between the layers. This seems to be very
interesting,
however, no result is published.

I believe that 3d-kriging does not bring much, however, the comparisons
between
the structures of the layers are very challencing.
...)

Denis Marcotte <Denis.Marcotte@...>:
(...
It is probably better to treat this kind of data as 2D, soil type by soil
type. You can krige the thickness of each soil type and also the measured
variables; this will allow you to reconstruct vertical sections
everywhere. The data probably shows a complicated trend along the vertical
profile which complicates seriously the 3D study.
...)

Med Bennett <mbennett@...>:
(...
I would compute a vertical or "downhole" variogram to see if there if any
significant spatial correlation in that direction. If so, you should
attempt to use a 3D kriging method, as it would be wasteful not to use
that
information. You will have to use a very high value for anisotropy in the
Z direction (on the order of 1000 probably) or else leave the depth units
as cm and the horizontal units in m.
...)

"Nel, Fanie" <fnel@...>:
(...
I would suggest that you only krig within a horizon , not across horizons.
This assumes that the variables behave diffrently in each horizon. You
will
also have to estimate the width of each horizon.

If a variable shows a different variograms vertically and horizontally you
should do 3D kriging.
...)

I hope there all who wrote to me listed above (there is some chaos in my
Mailbox these days).

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Markus Böhm
Groner Landstr. 45
D-37081 Goettingen

fon: +49 (0)551 / 5317388
fax: +49 (0)180 / 01212 5 109 12 817
mail: 1) mboehm@...-goettingen
2) boehm.m@...
url: http://www.stud.uni-goettingen.de/~mboehm

On Thu, 7 Jun 2001, Markus Boehm wrote:

> Dear all,
>
> how should soil data (~3300 profiles, ~150m average horizontal distance,
> all about 1 meter deep with different thickness of horizons representing
> type of soil, humus contents, ...) be kriged?
>
> I need all information of the different horizons to calculate the somewhat
> like ground water infiltration rate.
>
> Does it make sense to use 3D-kriging methods? I think then there should a
> modification of the z-coordinate be made. I mean stretching of the
> z-coordinate. Does anyone know how to deal with the problem or some useful
> textbook?
>
> Or would you prefer to do 2D-kriging for a number of depths (10cm,
> 20cm,...), so there's no need to modify the z-coordinate?
>
>
> Regards,
> Markus
>
>
> --
> * To post a message to the list, send it to ai-geostats@...
> * As a general service to the users, please remember to post a summary of any useful responses to your questions.
> * To unsubscribe, send an email to majordomo@... with no subject and "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list
> * Support to the list is provided at http://www.ai-geostats.org
>

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