This command assigns grid files to strata names in sequence.
This list of grid files represents the geologic model of the
strata. The Make Strata Grid File or Auto-Run Strata Grids commands
can be used to create the grids before running this routine. The
Geologic Model grid assignments are stored in a user-specified file
name with the .pre file extension. There are two types of Geologic
Model files: elevation and thickness. When creating a new Geologic
Model file, you have the choice between elevation and thickness.
Once the Geologic Model file is created, the type cannot be
changed.
For elevation type Geologic Model files, the grid files define
the bottom elevation surface model for the corresponding strata. A
grid file for the ground surface model is also assigned in this
routine. The surface grid can be created with the Make 3D Grid File
routine in the Civil Design module. When the Geologic Model file is
applied in StrataCalc volume calculations, the strata thickness is
determined by comparing the current strata bottom elevation grid
with previous upper strata or surface grid. Shown below is an
elevation example.
With thickness type Geologic Model files, the grid files
represent the thickness for the corresponding strata. A surface
grid file is not specified. Without the ground surface elevation
grid, the StrataCalc routines cannot find outcrops or adjust the
strata thickness for variations on the surface. So the thickness
grids that you supply the Geologic Model file must account for the
outcrops and ground surface variations. To account for outcrops,
you can set the thickness grids to zero in outcrop areas by using a
closed polyline for the outcrop areas and running Grid File
Utilities-Set Value with the Use Inclusion Areas option. A
thickness model will not draw proper Fence Diagrams. To account for
surface variations, you can make a grid of the ground surface and a
bottom elevation grid of the top strata overburden. Then use Grid
File Utilities to subtract the top strata elevation grid from the
ground surface. The resulting difference grid is the top strata
thickness. Shown below is a thickness example.
All these grid files should have the same location and
resolution. They can vary for some commands, such as Surface Mine
Reserves. To ensure the same grid position, use the File
option at the Use position from another file or pick grid
position prompt when making the grid files. The model grids are
specified in the dialog shown below. The surface grid is defined in
the top of the dialog. To assign the surface grid, pick the Select
Grid File button in the upper right. Next there is a list of the
strata names and the corresponding grid files. To add a strata grid
assignment, highlight the strata above the one to add and click the
Add button. This brings up the next dialog where you enter
the strata name and grid file. Besides elevation and thickness
grids, attribute grids such as BTU can be assigned to the strata
names. In the Geologic Model Grid Definition dialog, click on the
Attribute toggle and enter the Attribute Name. The strata in this
list should be listed in top to bottom order. If a strata is out of
order, highlight the strata in the list and click the Move
Up or Move Down button. The Auto-Complete option
looks for patterns in the existing grids to fill out grids for
another strata. For example, if the list of grids already has grids
for strata C1 of C1_bottom.grd and C1_BTU.grd, then when adding a
new strata named C2, the Auto-Complete will look for C2_bottom.grd
and C2_BTU.grd and automatically add these to the list.
The Load Auto-Run button will prompt you to select an Auto-Run Grid Definition File (.run). The program will then read the strata names from this file and build the Geologic Model Definition list. The Reset Directory button allows you to reassign the grid files directory in case the grid files have move since the Geologic Model file was created. Select the grid file at the top of the window, usually the first grid on the list. The surface grid will have to be redirected separately. The Extrapolate will extrapolate and save all the grids to remove NULL values. This option will save time in StrataCalc routines that use the Geologic Model file and extrapolate the grids on-the-fly each time. There is an option to extrapolate by merging or flattening (pancaking) elevation grids with upper strata. The "pancaking" is an option using the Extrapolate function. It will assign the Nulls in a grid the elevation of the strata above. This change is saved to the .GRD file. The other option will just extrapolate the grid elevation out to the grid limits.
The purpose of this routine is to allow you to process stored grids in routines such as Surface or Underground Reserves and Fence Diagram. These commands have a Geologic Model option under the modeling methods. Otherwise these routines will read selected drillholes and calculate the strata models on-the-fly. The advantage to the Geologic Model is that you have more control over each of the geologic model grids. After creating the strata grid file, there are many routines that can be used to analyze and modify the grids to make sure that the grids model the strata the way that you want, and even create a mining model from modifying the geologic grids. For example, you can use Plot 3D Grid File, Grid File Utilities and Contour from Grid in the Civil Design module.
Finally, for users with the Ore Module that have created block models, they may be added into the Geologic Model for use with the Fence Diagram and Surface Reserves commands. There is an option, next to Elevation or Attribute for Block Model. The procedure here is to build the Geologic Model, interval by interval from the top down as usual. Then add in the block model for each interval, or strata that you have. It is just like the other attributes, in that it must have the same name as the strata it is referring to. There are options on the Fence Diagram and Surface Reserves screens to use the hatch fence by block model and to break out quantities by attributes.
Pulldown Menu Location: StrataCalc
Keyboard Command: precalc