Building A Hierarchy With The Layer Thickness Method

Building A Hierarchy with the Layer Thickness Method

Open the Az-El panel for the viewer and set the elevation to zero and you should see the picture below.

$image\simple_hierarchy_flat.jpg$

Notice that this is a relatively flat geology without any lenses or pinch-outs. Because of this, the Layer Thickness method is a simple, effective way to specify our hierarchy. Slowly drag the Distance Slider to its maximum extent.

$image\layer_thickness_distance.jpg$

Your view should now look like the following image:

$image\layer_thickness_view.jpg$

Notice that when the TIN intersection point reaches a different material it stops moving, this does not mean that the bottom of the layer has been fully defined, it has just been defined at that point. The maximum distance on the slider should generally be used unless trying to define a lens or pinch-out. Select the Write Surface button again.

Notice that the distance has been reset to zero and the selected material type is now "1: Silt".

$image\layer_thickness1.jpg$

This is the only material option for this layer. Click the double down arrow button below the distance slider to completely define the bottom of the next layer. The maximum distance in this case is 20 which corresponds to the maximum thickness of the Silt layer being created.

$image\layer_thickness2.jpg$

Select the Write Surface button to write this surface to the GMF file.
The next surface is "Clay", click the double down arrow button below the distance slider to completely define the bottom of the layer. The layer should look like the one below.

$image\layer_thickness3.jpg$

Select the Write Surface button to write this surface to the GMF file.
The next surface is "Gravel", click the double down arrow button below the distance slider to completely define the bottom of the layer. The layer should look like the one below.

$image\layer_thickness4.jpg$

Select the Write Surface button to write this surface to the GMF file.
The next surface is "Sand", slowly drag the distance slider to its maximum extent. Since your PGF file represents raw boring logs, it is sometimes the case that the bottom of each boring corresponds to the maximum logging depth and not the true bottom of the last material. To define the bottom of model at the bottom of each boring would be artificially thinning the thickness of the last material by some unknown amount. In most cases you may know that the bottom of each boring is in fact the bottom of that last material OR if it is not you may still want to define the last surface in your model corresponding to the deepest depth for each boring where geologic data was collected. The default behaviour for the module is to use (preserve) the bottom of each boring that defines the bottom surface. This behaviour may be changed by unselecting the "Preserve Bottom" toggle.

$image\layer_thickness6.jpg$

For our example we will leave the bottom surface undefined, so unselect the Preserve Bottom toggle, make sure the distance slider is at its maximum extent and then select Write Surface. It is important to write out the bottom surface even when all borings have been dropped from it. The last surface in the GMF file should look like the following :

Surface 4 "Sand"

# ND_FOR_GEO 11566.299805 12850.599609 short "B-30"

# ND_FOR_GEO 11586.299805 13050.599609 short "B-31"

# ND_FOR_GEO 11086.299805 13090.599609 short "B-32"

# ND_FOR_GEO 11286.799805 13026.700195 short "B-59"

# ND_FOR_GEO 11393.500000 12948.900391 short "B-60"

# ND_FOR_GEO 11251.299805 12929.299805 short "B-75"

Note the "#" symbol at the beginning of each line, this symbol is universal in all of EVS file formats and will cause these lines to be treated as comments, so in the case of the GMF file it is as if these lines do not exist. When the last surface is written or the Finish Geology button is pressed the GMF file will be converted into a GEO file. In this conversion process the "# ND_FOR_GEO" flag will given a "short" value in the GEO file. The purpose of this value is discussed in the file format help for GEO files.

At this point, we have created both a .GEO and .GMF file representing the hierarchical geologic layers associated with our PGF file. In the next topic we will look at a much more complex PGF file and ultimately view the surfaces that we've created.