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Molly

Creating a surface for the uppermost elevations of a selected G value in a solid model

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A client recently asked about the sequence of steps to follow in finding the uppermost occurrences of a particular G value in his solid model and generating an elevation surface (GRD file) to represent this.

The solution requires these steps:

1. Use the Utilities / Solid / Filter / Range Filter tool to filter the MOD file for all G values greater than the desired G value. (Activate the High-Stop/Low-Pass option, set the threshold to the desired G value and the replacement to the null value.) The result will be that the desired G value is now the greatest value in the model.

2. Use the Utilities / Solid / Convert / Solid -> Grid tool to read the filtered MOD file and generate a surface representing the uppermost elevation of the highest G value. (Activate the Highest Elevation of Highest G Value option.) The result will be a GRD file which can be displayed as a 2D contour map and/or 3D surface.

post-3-042084300 1311870741_thumb.jpg

Molly Mayfield

RockWare Inc

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I'm interested in finding the uppermost surface of a solid model regardless of a particulare G-value.

I've built a lithology solid model with Boreholes data AND a topographic map.

If I choose Lithology Surface Map I don't get the contour map because only a single cell is visible (elevation > topographic grid elevation - Fig forum-01-solid model surface map 1.jpg)

If I offset the topographic grid by -0.5 m and create a new Lithology surface map I get all cell visible (sorry but there is an error in uploading this file even if the size is smaller than requested - This file was too big to upload).

In Fig. forum-01-solid model profile.jpg you can see a solid model profile (the red line is the topographic profile).

How can I get the uppermost surface of the solid model in order to get the surface map?

Thank you.

DLattuada

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Hi Daniele,

I'm a little confused - don't you already have a topographic surface which you used to constrain the lithology model (setting nodes above ground to null), and which you're using in the Lithology Surface map program?

Anyway, some background:

- The Lithology / Surface Map program is designed to extract the lithology material type from a solid model, along the designated ground surface model. So, the Z values in the resulting grid model represent lithotypes (1's, 2's, 3's, etc.), NOT elevations.

- The Lithology / Superface (Top) program is designed to create an elevation grid of the uppermost occurrence of a specific lithology type

So, if you simply want to create an elevation grid to reflect the elevations of the uppermost nodes of your lithology block model, regardless of the actual material there, I would do the following:

1. Create a Boolean model of your Lithology MOD file, setting the Thresholds to include all possible lithotypes (such as 1 - 5). (Utilities: Solid / Boolean Operations / Boolean Conversion) The result will be a Boolean solid model in which all voxels with lithotypes are now "1"s.

2. Use the Solid / Convert / Solid -> Grid to determine the Highest Elevation of the Highest G-Value. This will generate a grid model with elevations that correspond to the uppermost lithology nodes in the solid model.

Note that the accuracy of the resulting grid (and the accuracy of your lithology model, for that matter) will be dependent on the vertical spacing of your solid model nodes. Be sure the Z spacing is small enough to honor tight lithology intervals, but not so small that you'll grow old as the model is generated.

Hope this helps

Molly Mayfield

RockWare Inc.

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I'm a little confused - don't you already have a topographic surface which you used to constrain the lithology model (setting nodes above ground to null), and which you're using in the Lithology Surface map program?

I'm too. I'm using the same topographic surface.

Anyway, some background:

- The Lithology / Surface Map program is designed to extract the lithology material type from a solid model, along the designated ground surface model. So, the Z values in the resulting grid model represent lithotypes (1's, 2's, 3's, etc.), NOT elevations.

I'm looking to get the lithotypes outcrops, as I could see from an aerial photo.

In Lithology Surface Map, setting the topographic surface, I get the attached figure [forum-01-solid model surface map 1.jpg].

I finally get what I was looking for, following you step by step instructions: 1) Boolean Model, 2) Solid Model / Convert / Solid -> Grid (Highest Elevation of the Highest G-Value) and 3) Lithology Surface Model with the new Grid Model Elevation retrieved from the Solid Model (Attached file: [02-outcrops-boolean.jpg]).

I also rebuild the solid model setting the Buffer size to 0 in the Upper Surface (Grid) Filter.

- The Lithology / Superface (Top) program is designed to create an elevation grid of the uppermost occurrence of a specific lithology type

OK

Note that the accuracy of the resulting grid (and the accuracy of your lithology model, for that matter) will be dependent on the vertical spacing of your solid model nodes. Be sure the Z spacing is small enough to honor tight lithology intervals, but not so small that you'll grow old as the model is generated.

Ok, I've set the Z spacing according to the resolution of the lithology intervals.

Regards,

DLattuada

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