Another way would be to use grass to generate surfaces or horizon based
on individual layer picks from the logs and use a script to convert
them to vtk format. For one thing vtk is written in python and grass
can import vtk. I'm attaching an example of what i get. In all fairness i used R and paraview (based on vtk libraries) but the whole procedure can easily be ported to GRASS.<br><br><div class="gmail_quote">On Sat, Jan 9, 2010 at 12:51 PM, Dylan Beaudette <span dir="ltr"><<a href="mailto:dylan.beaudette@gmail.com">dylan.beaudette@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">On Sat, Jan 9, 2010 at 2:51 AM, Benjamin Ducke<br>
<div class="im"><<a href="mailto:benjamin.ducke@oxfordarch.co.uk">benjamin.ducke@oxfordarch.co.uk</a>> wrote:<br>
</div><div class="im">> Cheers for these. They are certainly all highly interesting.<br>
> Do you have an actual link for the T-PROGS software itself?<br>
> All I can seem to come up with are interfaces from other<br>
> software and publications mentioning it.<br>
><br>
> I would certainly be interested in taking a look at your<br>
> GRASS interface. Is T-PROGS open source?<br>
><br>
> My gut feeling is that the T-PROGS approach would give better<br>
> results than 3D kriging, as it seems better able to to<br>
> follow 3D shape trends:<br>
><br>
> <a href="http://chl.erdc.usace.army.mil/chl.aspx?p=s&a=ARTICLES;37&g=50" target="_blank">http://chl.erdc.usace.army.mil/chl.aspx?p=s&a=ARTICLES;37&g=50</a><br>
><br>
> ... but that certainly would need testing.<br>
><br>
> Having said that, I also like this approach for a more<br>
> heuristic model:<br>
><br>
> <a href="http://chl.erdc.usace.army.mil/chl.aspx?p=s&a=ARTICLES;41&g=50" target="_blank">http://chl.erdc.usace.army.mil/chl.aspx?p=s&a=ARTICLES;41&g=50</a><br>
><br>
> It's very simple and could easily be implemented directly<br>
> in GRASS GIS. In fact, I coded something very similar to this<br>
> for archaeological stratigraphy reconstruction a while back.<br>
><br>
> Cheers,<br>
><br>
> Ben<br>
<br>
</div>Hi Ben,<br>
<br>
Yes. It would be very interesting to have these functions within GRASS<br>
libraries, as opposed to the kludgy interfacing that I did via shell<br>
scripting + awk. Here are some of the details, from *several* years<br>
ago (GRASS 5.x):<br>
<br>
<a href="http://169.237.35.250/%7Edylan/grass_and_tp/" target="_blank">http://169.237.35.250/~dylan/grass_and_tp/</a><br>
<br>
... note that this is rather old work, and somethings may have changed<br>
since then.<br>
<br>
Here is the reference for the software:<br>
<br>
Carle, Steven F. T-PROGS Transition Probability Geostatistical<br>
Software Version 2.1 manual. University of California, Davis. 1999.<br>
<br>
I can get in touch with Graham Fogg here at UC Davis, whom I believe<br>
is in charge of maintaining the current implementation of T-PROGS--<br>
basically fortran source + a tcl/tk interface. Having this<br>
functionality in GRASS would greatly add to the capabilities of the<br>
voxel framework.<br>
<br>
Also, by 'conditional simulation' I wasn't referring to kriging per<br>
se, rather the conditional simulation of an indicator (categorical)<br>
variable, based on random fields + variogram model. the gstat library<br>
can perform both unconditional simulation (randomness only tied to a<br>
variogram model), and conditional simulation (randomness tied to real<br>
point data + variogram model) .<br>
<br>
I'll report back here with my findings.<br>
<br>
Cheers,<br>
<font color="#888888">Dylan<br>
</font><div><div></div><div class="h5"><br>
<br>
<br>
><br>
><br>
> ----- Original Message -----<br>
> From: "Dylan Beaudette" <<a href="mailto:dylan.beaudette@gmail.com">dylan.beaudette@gmail.com</a>><br>
> To: "Benjamin Ducke" <<a href="mailto:benjamin.ducke@oxfordarch.co.uk">benjamin.ducke@oxfordarch.co.uk</a>><br>
> Cc: "GRASS user list" <<a href="mailto:grass-user@lists.osgeo.org">grass-user@lists.osgeo.org</a>><br>
> Sent: Saturday, January 9, 2010 4:30:40 AM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna<br>
> Subject: Re: [GRASS-user] Searching Docs about 3D geological modelisation<br>
><br>
> Two more ideas:<br>
><br>
> 1. conditional simulation, based on a 3D variogram model<br>
> 2. transition probability-based interpolation of categories<br>
><br>
> Check out gstat for the conditional simulation, and TPROGS for the<br>
> transition probability. If anything is interested, I have done some<br>
> programming to connect GRASS and TPROGS.<br>
><br>
> Cheers!<br>
><br>
> Dylan<br>
><br>
> On Fri, Jan 8, 2010 at 1:24 PM, Benjamin Ducke<br>
> <<a href="mailto:benjamin.ducke@oxfordarch.co.uk">benjamin.ducke@oxfordarch.co.uk</a>> wrote:<br>
>> Woohoo, this forum is always a treasure trove<br>
>> of good advice. I had not idea SGemS existed!<br>
>> The Voronoi idea is also good, I am just not sure<br>
>> that the 3D Voronoi diagram is quite what one<br>
>> would instinctively think it is.<br>
>><br>
>> <a href="http://en.wikipedia.org/wiki/Voronoi_diagram" target="_blank">http://en.wikipedia.org/wiki/Voronoi_diagram</a><br>
>><br>
>> says: "In general a cross section of a 3D Voronoi<br>
>> tessellation is not a 2D Voronoi tessellation itself."<br>
>><br>
>> Need to look into that.<br>
>><br>
>> I don't have much practical experience<br>
>> with Bayes models, so can't really comment on<br>
>> that.<br>
>><br>
>> Cheers,<br>
>><br>
>> Ben<br>
>><br>
>><br>
>> Christian Kaiser wrote:<br>
>>> It seems to me that this is a 3D interpolation problem with categorical variables.<br>
>>><br>
>>> 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: <a href="http://www.enge.ucl.ac.be/staff/curr/Bogaert/biblioBME/BMEbibsubject.html#Soil%20Science" target="_blank">http://www.enge.ucl.ac.be/staff/curr/Bogaert/biblioBME/BMEbibsubject.html#Soil%20Science</a><br>
>>><br>
>>> Or maybe you can have a look at SGeMS (<a href="http://sgems.sourceforge.net" target="_blank">http://sgems.sourceforge.net</a>), a tool for 3D geostatistics.<br>
>>><br>
>>> None of them is available through GRASS, but the algorithms are freely available (I think open-source, but not verified).<br>
>>><br>
>>> I am not a geologist, so please forgive if it is not adequate...<br>
>>><br>
>>> Christian Kaiser<br>
>>><br>
>>><br>
>>><br>
>>><br>
>>><br>
>>> On 8 janv. 2010, at 11:04, Benjamin Ducke wrote:<br>
>>><br>
>>>> Rich Shepard wrote:<br>
>>>>>> material. There is no interpolation algorithm in GRASS currently which<br>
>>>>>> can<br>
>>>>>> handle that sort of data well.<br>
>>>>> So what is needed is a political algorithm. :-)<br>
>>>> That's actually right: given the presence of n different<br>
>>>> layer types in the vicinity of an empty voxel, the algorithm<br>
>>>> would need to decide by some sort of "majority vote"<br>
>>>> which type to assign to that voxel.<br>
>>>><br>
>>>>> Kidding aside, I suspect that a fuzzy interpolation algorithm would solve<br>
>>>>> the problem.<br>
>>>> How? You could make the interpolated value depend on a<br>
>>>> fuzzy set member function, I suppose, but the situation<br>
>>>> here is actually so well defined that I think a probabilistic<br>
>>>> approach would be preferable. Since each voxel can only<br>
>>>> store one value, a second output map could store the<br>
>>>> classification probability. That may be very useful<br>
>>>> for visualization (you could show voxels with little<br>
>>>> probability hazier).<br>
>>>><br>
>>>> Ben<br>
>>>><br>
>>>>> Rich<br>
>>>>> _______________________________________________<br>
>>>>> grass-user mailing list<br>
>>>>> <a href="mailto:grass-user@lists.osgeo.org">grass-user@lists.osgeo.org</a><br>
>>>>> <a href="http://lists.osgeo.org/mailman/listinfo/grass-user" target="_blank">http://lists.osgeo.org/mailman/listinfo/grass-user</a><br>
>>>>><br>
>>>>><br>
>>>><br>
>>>> --<br>
>>>> Benjamin Ducke<br>
>>>> Geospatial Consultant<br>
>>>><br>
>>>> Oxford Archaeology Digital<br>
>>>> Janus House<br>
>>>> Osney Mead<br>
>>>> OX2 0ES<br>
>>>> Oxford, U.K.<br>
>>>><br>
>>>> Tel: +44 (0)1865 263 800 (switchboard)<br>
>>>> Tel: +44 (0)1865 980 758 (direct)<br>
>>>> Fax :+44 (0)1865 793 496<br>
>>>> <a href="mailto:benjamin.ducke@oadigital.net">benjamin.ducke@oadigital.net</a><br>
>>>> <a href="http://oadigital.net" target="_blank">http://oadigital.net</a><br>
>>>><br>
>>>><br>
>>>><br>
>>>><br>
>>>><br>
>>>> ------<br>
>>>> Files attached to this email may be in ISO 26300 format (OASIS Open Document Format). If you have difficulty opening them, please visit <a href="http://iso26300.info" target="_blank">http://iso26300.info</a> for more information.<br>
>>>><br>
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>>> _______________________________________________<br>
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>>><br>
>>><br>
>><br>
>><br>
>> --<br>
>> Benjamin Ducke<br>
>> Geospatial Consultant<br>
>><br>
>> Oxford Archaeology Digital<br>
>> Janus House<br>
>> Osney Mead<br>
>> OX2 0ES<br>
>> Oxford, U.K.<br>
>><br>
>> Tel: +44 (0)1865 263 800 (switchboard)<br>
>> Tel: +44 (0)1865 980 758 (direct)<br>
>> Fax :+44 (0)1865 793 496<br>
>> <a href="mailto:benjamin.ducke@oadigital.net">benjamin.ducke@oadigital.net</a><br>
>> <a href="http://oadigital.net" target="_blank">http://oadigital.net</a><br>
>><br>
>><br>
>><br>
>><br>
>><br>
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>> Files attached to this email may be in ISO 26300 format (OASIS Open Document Format). If you have difficulty opening them, please visit <a href="http://iso26300.info" target="_blank">http://iso26300.info</a> for more information.<br>
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><br>
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