Why not just ask Steve what he is concerned about and
what he would like us to do so that he can shed his
concerns?
And then try to find a way to accommodate him?
If he got more directly involved into this process,
it might make him feel less uneasy about it.
Ben
----- Original Message -----
From: "Dylan Beaudette" <debeaudette@ucdavis.edu>
To: grass-user@lists.osgeo.org
Cc: "Benjamin Ducke" <benjamin.ducke@oxfordarch.co.uk>, "Graham Fogg" <gef52@mac.com>
Sent: Friday, January 22, 2010 9:38:18 PM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna
Subject: Re: [GRASS-user] Searching Docs about 3D geological modelisation
On Saturday 09 January 2010, Benjamin Ducke wrote:
Cheers for these. They are certainly all highly interesting.
Do you have an actual link for the T-PROGS software itself?
All I can seem to come up with are interfaces from other
software and publications mentioning it.
I would certainly be interested in taking a look at your
GRASS interface. Is T-PROGS open source?
My gut feeling is that the T-PROGS approach would give better
results than 3D kriging, as it seems better able to to
follow 3D shape trends:
http://chl.erdc.usace.army.mil/chl.aspx?p=s&a=ARTICLES;37&g=50
... but that certainly would need testing.
Having said that, I also like this approach for a more
heuristic model:
http://chl.erdc.usace.army.mil/chl.aspx?p=s&a=ARTICLES;41&g=50
It's very simple and could easily be implemented directly
in GRASS GIS. In fact, I coded something very similar to this
for archaeological stratigraphy reconstruction a while back.
Cheers,
Ben
Hi Ben and others,
Here are some concerns from the author of the TPROGS software:
---------------------------------------------------------------------------------------------------------
Steve is hesitant because he's not sure what the finished product would be. I
think he's probably concerned about misapplication or perhaps some kind of
ripoff. Can you provide a bit more background on where you see this going?
---------------------------------------------------------------------------------------------------------
I think that it would be helpful to put together a small proposal, regarding
how the TPROGS source code / ideas would be integrated into GRASS. It seems
like the author is worried about use without citation, and once he
understands what GRASS developers have in mind, should be for it.
To start the discussion, I propose that the methods used within the TPROGS
software be integrated (with proper citations) into a GRASS library, so that
a series of modules can perform the multi-step process associated with
modeling transition probabilities. Furthermore, the GRASS rast3 (voxel)
datatype should be used to store the resulting structures-- this will make
visualization with NVIZ / Paraview a snap.
Alternatively, we may be able to link GRASS with TPROGS with a little bit of
python glue. While this may work if there are limitations regarding the use
of the TPROGS source, I think that having these algorithms present in the
GRASS libraries would be a real benefit.
I have CC-ed Graham, so that we can keep him in the conversation.
Cheers,
Dylan
----- Original Message -----
From: "Dylan Beaudette" <dylan.beaudette@gmail.com>
To: "Benjamin Ducke" <benjamin.ducke@oxfordarch.co.uk>
Cc: "GRASS user list" <grass-user@lists.osgeo.org>
Sent: Saturday, January 9, 2010 4:30:40 AM GMT +01:00 Amsterdam / Berlin /
Bern / Rome / Stockholm / Vienna Subject: Re: [GRASS-user] Searching Docs
about 3D geological modelisation
Two more ideas:
1. conditional simulation, based on a 3D variogram model
2. transition probability-based interpolation of categories
Check out gstat for the conditional simulation, and TPROGS for the
transition probability. If anything is interested, I have done some
programming to connect GRASS and TPROGS.
Cheers!
Dylan
On Fri, Jan 8, 2010 at 1:24 PM, Benjamin Ducke
<benjamin.ducke@oxfordarch.co.uk> wrote:
> Woohoo, this forum is always a treasure trove
> of good advice. I had not idea SGemS existed!
> The Voronoi idea is also good, I am just not sure
> that the 3D Voronoi diagram is quite what one
> would instinctively think it is.
>
> http://en.wikipedia.org/wiki/Voronoi_diagram
>
> says: "In general a cross section of a 3D Voronoi
> tessellation is not a 2D Voronoi tessellation itself."
>
> Need to look into that.
>
> I don't have much practical experience
> with Bayes models, so can't really comment on
> that.
>
> Cheers,
>
> Ben
>
> Christian Kaiser wrote:
>> It seems to me that this is a 3D interpolation problem with categorical
>> variables.
>>
>> Maybe the Bayesian Maximum Entropy approach could help. There are some
>> interesting publications around also for geology and soil sciences, and
>> they can deal with categorical data as well. Look for example here:
>> http://www.enge.ucl.ac.be/staff/curr/Bogaert/biblioBME/BMEbibsubject.htm
>>l#Soil%20Science
>>
>> Or maybe you can have a look at SGeMS (http://sgems.sourceforge.net), a
>> tool for 3D geostatistics.
>>
>> None of them is available through GRASS, but the algorithms are freely
>> available (I think open-source, but not verified).
>>
>> I am not a geologist, so please forgive if it is not adequate...
>>
>> Christian Kaiser
>>
>> On 8 janv. 2010, at 11:04, Benjamin Ducke wrote:
>>> Rich Shepard wrote:
>>>>> material. There is no interpolation algorithm in GRASS currently
>>>>> which can
>>>>> handle that sort of data well.
>>>>
>>>> So what is needed is a political algorithm. 
>>>
>>> That's actually right: given the presence of n different
>>> layer types in the vicinity of an empty voxel, the algorithm
>>> would need to decide by some sort of "majority vote"
>>> which type to assign to that voxel.
>>>
>>>> Kidding aside, I suspect that a fuzzy interpolation algorithm would
>>>> solve the problem.
>>>
>>> How? You could make the interpolated value depend on a
>>> fuzzy set member function, I suppose, but the situation
>>> here is actually so well defined that I think a probabilistic
>>> approach would be preferable. Since each voxel can only
>>> store one value, a second output map could store the
>>> classification probability. That may be very useful
>>> for visualization (you could show voxels with little
>>> probability hazier).
>>>
>>> Ben
>>>
>>>> Rich
>>>> _______________________________________________
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>>>
>>> --
>>> Benjamin Ducke
>>> Geospatial Consultant
>>>
>>> Oxford Archaeology Digital
>>> Janus House
>>> Osney Mead
>>> OX2 0ES
>>> Oxford, U.K.
>>>
>>> Tel: +44 (0)1865 263 800 (switchboard)
>>> Tel: +44 (0)1865 980 758 (direct)
>>> Fax :+44 (0)1865 793 496
>>> benjamin.ducke@oadigital.net
>>> http://oadigital.net
>>>
>>>
>>>
>>>
>>>
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>>
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>
> --
> Benjamin Ducke
> Geospatial Consultant
>
> Oxford Archaeology Digital
> Janus House
> Osney Mead
> OX2 0ES
> Oxford, U.K.
>
> Tel: +44 (0)1865 263 800 (switchboard)
> Tel: +44 (0)1865 980 758 (direct)
> Fax :+44 (0)1865 793 496
> benjamin.ducke@oadigital.net
> http://oadigital.net
>
>
>
>
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Soil Resource Laboratory
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University of California at Davis
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