This command will create a drillhole from an electronic log of
gamma ray and density readings that vary with depth, but other
attributes may also be used for strata classification. These eLog
files have an .las file extension, which should not be confused
with point cloud scans that sometimes use the same file extension.
It is important to note that gamma/density surveys can vary greatly
by equipment, and input settings will likely need to be calibrated
to the equipment and project.
When the command is executed, the below dialog will
appear.
To create a drillhole from an .las file, the following steps
should be taken:
Y-Axis/X-Axis Field: These dropdown menus set the
attributes to display on each axis of the strata classification
chart shown in the middle of the dialog. The dropdown menus will
only be populated after selecting fields with the Choose
Fields button. These fields only affect the visualization of
the strata classification table and do not affect how the strata
are actually classified.
Depth Field Header: This dropdown menu sets the attribute
to use for the Depth of the drillhole.
Assign Unidentified Material to Strata Above: This
checkbox controls the classification of strata that do not fit into
the strata classification table. When this option is enabled,
unidentified strata will be assigned to the strata above it. When
this option is disabled, unidentified strata will be assigned a
name according to the Unidentifiable Strata Name
field.
Unidentifiable Strata Name: This field sets the name for
strata that do not fit into the strata classification
table.
Filter Options: These options will filter the .las file
to remove noise in the gamma/density readings. If the strata
classification changes in an unrealistic manner, filtering the data
may correct the problem.
The None option will not filter the input data.
The Low, Medium, and High options will filter the data more and more aggressively. When these filters are used, it is recommended to thoroughly check the output for accuracy.
The strata classification table is the spreadsheet at the bottom of
the dialog. This table classifies each section of the drillhole to
a strata according to min/max values of the density, gamma
readings, and other attributes. This table should only be modified
after selecting fields with the Choose Fields button. Strata
may be added, removed, and sorted using the green icons to the
right of the table. Here it is important to note that strata listed
higher in the table will take precedence over strata on lower rows.
In other words, if a section of the drillhole matches the criteria
for multiple strata, it will be assigned to the first strata listed
in the classification table. This concept is visualized in the
classification chart. For example, in the above image, there is
some overlap between the criteria for Coal and for Clay. Since Coal
is listed at the top of the classification table, the black box in
the chart representing Coal is drawn over the red box representing
Clay.
Select: This column controls if the strata is used for classification. If this option is set to No, the respective strata will not appear in the drillhole.
Name: This column sets the name for each strata.
Color: This column sets the color for each strata in the classification chart. This color is not used for any other purpose. Colors may be set by clicking the ellipse button to the right of this column.
Attribute Min/Max: These columns will be set according to the fields found in the .las file. Each column sets a bounding value for the strata. In the example shown in the above image, strata to be classified as Coal must have a density between 1.28 and 1.85 (note that these values are actually expressed as specific gravity) and a gamma reading between 40 and 115.
Description: This optional column can be used as a descriptor of the strata. This description will not be stored in the drillhole, however.
Create: This button will create a drillhole from the
current .las file. When clicked, you will be prompted to select a
location for the drillhole.
Load/Save Settings: These options will load/save settings
to a .gd file.
Choose Fields:This button will prompt you for an .las
file. The attribute headers found in the .las file will be added to
the strata classification table.
Load eLog: This button will prompt you for an .las file.
The drillhole will be classified according to the strata
classification table and a preview of the results will be shown on
the right side of the dialog.