The Grade-Thickness Calculation Sub-Menu appears below:

- Return To Main Menu
- Command Shell
- Calculate Grade-thickness
- Triangulate Grade-thickness
- Grade-thickness Value Presort
- Grade-thickness Modeling
- Graphical Display of Grade-thickness
- Create Grade Thickness from 3-D Grade Model

This module enables the user to calculate grade-thickness (G-T) values for a given set of rock or seam codes, and graphically display the results. This module is useful for obtaining a general feel for grade continuity and depositional trends for a given set of rock units or seams.

The user creates a file of grade-thickness values for a given set of rock or seams that is based on the current drillhole assay label. These values can then be displayed in plan view, or a 2-dimensional grid file can be created so that a contour plot of the grade-thickness values can be displayed.

This menu choice enables the user to invoke commands and run external programs without exiting MicroMODEL. This program is simply a command shell. The user enters as many commands as desired. Type "EXIT" at the command prompt to return to MicroMODEL.

This menu choice runs the program that creates a grade-thickness data set for a given rock code. The grade-thickness data set includes the following items of information for each drillhole containing at least one assay interval of the selected rock code:

- Drillhole Name
- Grade-thickness value
- Easting and Northing of G-T centroid

The method by which grade-thickness values are calculated is based on standard geologic practices. For vertical holes with no deviation, the calculation is conceptually straightforward. For angle holes, or vertical holes that deviate, the concept is more complex. For each drillhole, all sample intervals of the selected rock or seam type(s) are examined. For each sample interval, a grade-thickness is calculated as follows:

- The vertical projection of the sample interval is calculated. This is the difference in elevation between the top and bottom of the interval. This vertical thickness is multiplied by the grade for that sample interval to compute a grade-thickness value. Grade-thickness values for each sample interval are added together to compute the grade-thickness value for the hole (for the chosen rock code). Note that missing values are not counted in the calculation; any intervals with missing assays are excluded from the grade-thickness calculation.
- The easting and northing value for each grade-thickness value is calculated based on an interval-length weighted centroid value. For each sample interval, the midpoint easting and northing are taken and multiplied by the interval length. The interval length times easting (northing), as well as the interval length are summed. The easting (northing) of the grade-thickness centroid is then calculated by dividing the sum of (interval-length x coordinate) and dividing by the total interval length.
- In cases where a drillhole assay interval straddles a downhole survey break, the assay interval is split into two smaller intervals with identical assay values before calculating the grade-thickness, using the survey break as the dividing point.

This program creates a Surface or Thickness model using the method of Delaunay Triangles. Data points must alreay have been created using 8.3 Calculate Grade Thickness Values.

The user can opt to model a subset of the project by choosing starting and ending column and row limits. Then, the surface(s) to be modeled is chosen. Finally, the user may opt to generate a POLY.CNT style output file that contains the triangles that are constructed. The triangles are written to a file whose name must be entered by the user. The triangles may be displayed using choice 2.3.5, "Plot Digitized Data in Plan View."

Once the triangles are constructed, the program loops through the column and row ranges that were specified. For each grid cell that falls inside a triangle, an elevation is calculated based on the elevations of the three corners of the triangle. Since these corner points define an imaginary plane in space, it is a simple matter to calculate the elevation of the imaginary plane at the 2-D grid centroid location.

Note that the program does not reset the value of grid points located outside of any constructed triangles. The user should delete the 2-D surface or thickness data file prior to running this program if the grid points need to be reset.

The Grade-Thickness Modeling option (Section 8.6) assigns a grade-thickness value to each cell of a 2-dimensional grid according to user specified constraints. Before the user can proceed to modeling, the grade-thickness data (prepared in Section 8.3) must be presorted.

The Grade-Thickness Value Presort option presorts data for each grid cell center within user specified bounds. The advantage of separating the presorting and modeling routines is, that once presorting is accomplished, several modeling runs can be made on the same presorted file with a minimum of computer time.

It is not necessary to presort the grade-thickness data for each modeling run unless the data search (presort) parameters are changed.

Options available for grade-thickness presorting are exactly the same as those for surface modeling. The user should refer to MicroMODEL documentation Volume II, Section 2.7 for details.

This option allows the user to interpolate grade-thickness values into a regular 2-dimensional grid according to user specified parameters. The input data for this program is contained in the presorted grade-thickness data file created by the previous option, Grade-thickness Presort (Section 8.5).

The first time this program is run, a background grid of unestimated cell values (-999.99) is created. This background grid is then updated with the interpolated grade-thickness values by the Surface Modeling program. This updating may be an overwriting of the entire grid, or an overwriting of only a portion of the grid because of submodel clipping.

Two modeling options are available to the user, KRIGING and INVERSE DISTANCE TO A POWER (IDP). The grade-thickness modeling program has exactly the same options as the surface modeling program. The user should refer to MicroMODEL documentation Volume II, Section 2.8 for details.

This submodule allows the user to display the 2-dimensional grade-thickness grid that has been previously created by MicroMODEL. The Graphical Display Sub-Menu is organized as follows:

GRAPHICAL DISPLAY SUB-MENU

- Return To Submenu
- Command Shell
- Display Grade-thickness Points
- Contour Grid Values
- Plan View Cell Plot of Grid Values

The graphic output produced by the above options are:

- Grade-thickness Value Plot
- Contour Plot (scale map)
- Plan View Cell Plot (scale map)

This option allows the user to produce a plan view map (plot) of the grade-thickness data point locations. The map can be displayed at any user specified scale within the size limitations of the user's plotter. The user can design the plot to meet his specific needs, using the inputs described below.

Each grade-thickness data point within the user specified plot area is marked with a "+" symbol. Up to 4 lines of information can be plotted above the location symbol. The types of information that can be plotted in any user specified order are:

- Northing of Data Point
- Easting of Data Point
- Grade-thickness Value
- Drillhole Name

The line options are plotted from the location marker up, so the first line is plotted immediately above the marker, the second line plotted above the first line and so on.

Since some of the line option information requires decimal point display, the user can structure the output format by specifying the NUMBER OF CHARACTERS BEHIND THE DECIMAL when prompted. Refer to section 1.8 for more information.

With each LINE OPTION the user must specify a PEN NUMBER to be associated with that LINE OPTION.

The CHARACTER SIZE is specified by the user as a fraction of the row dimension. A character size of 0.25 results in plotted characters that have a height which occupies one quarter of the row dimension. See Volume I, Section 6.3.8 for more information on selecting character sizes. For further explanation on CHARACTER SIZE, see chapter 8, Plotting.

The user selects a PEN NUMBER for the data location mark. The PEN NUMBER is restricted by the plotter limitations.

The LOCAL GRID can be plotted over the plot according to three LOCAL GRID PLOTTING OPTIONS. Refer to section 1.8 for details.

If the LOCAL GRID is to be plotted, the user must specify a PEN NUMBER for the GRID NUMBERS and either a LOCAL GRID LINE PEN NUMBER or a TIC MARK PEN NUMBER and PERIMETER LINE PEN NUMBER. The character size for the grid numbers is a fraction of the cell dimension, and the character size of the Northings and Eastings is the same as for the drill hole identification information. For further explanation on LOCAL GRID OPTIONS, see chapter 11, Plotting.

The GLOBAL GRID can be displayed on the finished plot. The appearance of the GLOBAL GRID is governed by two GLOBAL GRID PLOTTING OPTIONS. Refer to Section 1.8 for details.

If the GLOBAL GRID is to be plotted, the user must specify a GLOBAL GRID INTERVAL in the project units (Feet or Meters) and a PEN NUMBER for the GLOBAL GRID LINES. The character size is the same as specified earlier. For further explanation on GLOBAL GRID OPTIONS, see chapter 8, Plotting.

Row and Column Clipping allows the user to plot a partial section (window) of the model area. The user defines this window with STARTING and STOPPING ROWS and COLUMNS as prompted by MicroMODEL. For further explanation on ROW and COLUMN CLIPPING, see chapter 8, Plotting.

The TITLE BLOCK parameters are set after all program parameters have been set. For a complete discussion of the TITLE BLOCK QUESTIONS, see chapter 11, Plotting.

The Surface Location Plotting program produces a scaled plot that can be output at any user specified map scale (see Volume I, Section 6.3.7). The SCALE OF THE PLOT determines the plot size in feet/inch or meters/meter. For screen preview, a plot scale of "P" (for Preview) is recommended. A plot scale of "S" suppresses the plotter output and returns the user to the menu system. For further explanation on SCALE OF PLOTS, see chapter 11, Plotting.

This option allows the user to produce contour maps of the current 2-dimensional grade-thickness grid. The user can design the contour maps as needed by invoking a variety of plotting options. The contour plots can be produced at any map scale.

This program works in exactly the same manner as the contouring program for surface topography. Refer to section 2.9.5 for details.

The Grade-thickness Contour Plotting program produces a scaled plot that can be output at any user specified map scale (see Volume I, Section 6.3.7). The SCALE OF THE PLOT determines the plot scale in either feet/inch or meters/meter. A plot scale of "P" is recommended for previewing plots on the computer screen. A plot scale of "S" suppresses the plot output and return the user to the plotter menu system. For further explanation on SCALE OF PLOTS, see Volume II, chapter 11, Plotting.

This option allows the user to produce contour maps of the current 2-dimensional grade-thickness grid. The user can design the contour maps as needed by invoking a variety of plotting options. The contour plots can be produced at any map scale.

This program works in exactly the same manner as the cell plot program for surface topography. It displays the Grade-thickness values in plan view. Refer to section 2.9.4 for details.

The Plan View Cell Plot program produces a scaled plot that can be output at any user specified map scale (see Volume I, Section 6.3.7). The SCALE OF THE PLOT determines the plot scale in either feet/inch or meters/meter. For further explanation on SCALE OF PLOTS, see Volume II, chapter 11, Plotting.

This option allows the user to create a Grade-thickness Model from a conventional 3-D grade model. This is a useful tool for investigating a modeling method.

The Grade-Thickness value for each cell is calculated by taking the sum of all grade blocks in that vertical column that meet the grade cutoff criteria and rock type criteria, and multiplying by the bench height.

The user must enter the ANSWER SET NAME, which identifies this run.

Next, the G-T CUTOFF GRADE is entered. For no cutoff, enter zero (0.0). Missing grade values are not included in the Grade-thickness calculation.

The user must choose the grade label and model type (polygon, IDP, kriged) for the 3-D model that contains values that will be used in the calculation. Note that a valid 3-D rock model file, R200, must also exist.

On the second input screen, the user enters the number of different rock types that will be included in the Grade-thickness calculation, and the individual rock codes.

Once the Grade-Thickness model has been created with this program, it can be displayed with any of the programs listed in section 8.7 of this chapter (Graphical Display of Grade-Thickness).