Indicator kriging

Indicator kriging is ordinary kriging of indicator-transformed data values for each of several cutoffs.  The result of performing indicator kriging is a Cumulative Frequency Function (CFF), stored as attributes in the block model.  In this way, indicator kriging is not creating a single value for the entire block, but rather describing the amount of material in the block above or below a given cutoff.

You must have previously created and documented variogram models and anisotropy parameters, such as as shown in the following table for this two-dimensional example.

Cutoff	Variogram	Bearing	Major/Semi-Major Anisotropy Ratio
1	cutoff10.vgm	0	2.0
2.5	cutoff25.vgm	22.5	3.0
5	cutoff50.vgm	22.5	2.3
10	cutoff100.vgm	0	2.1

 

For a three-dimensional example, you would have one additional column for major/minor anisotropy ratio.

Task: Perform indicator kriging

1. Choose Indicator kriging > Indicator kriging attribute ().
2. Enter the information as shown, and click Apply.



3. Choose Indicator kriging > Indicator kriging.
4. Enter the information as shown on each of the six following forms, and click Apply.

















5. Choose Display > Display block model.
6. Enter the information as shown, and click Apply.



7. Open gc_orezone1.con in Graphics.
8. Choose Attributes > View attributes for one block.
9. Select a block, to see its attributes.



The Cumulative Frequency Function (CFF) values have been estimated. New attributes have been created to store the CFF values, and are named _ikc#IKattribute#cutoff. In the image above, the value of 0.14 for the attribute _ikc#gold#5.0000 indicates that 14% of the block is estimated to fall below the value of 5.0.

Note: To see all of the steps performed in this task, run 2d_11e_ik_cff.tcl

Task: Calculate block values

1. Choose Indicator kriging > Block value estimates
2. Enter the information as shown on each of the four following forms, and click Apply.







3. On the Verify creation of file form, click Yes.
4. Choose Attributes View attributes for one block.
5. Select a block.



6. 

The block values have been calculated. Two new attributes have been created for each cutoff.

_ikb#IKattribute#cutoff_frac - the fraction of the block above the cutoff

_ikb#IKattribute#cutoff_value - the average grade of the block above that cutoff.

In addition, two other attributes are created.

_ikb#IKattribute#0.0000_frac - this will always be 1.00 = 100% of the block

_ikb#IKattribute#0.0000_value - the average grade of the entire block.

 In the image above, the value of 13.45 for the attribute _ikb#gold#0.0000 indicates that the average grade of the entire block is 13.45.

7. Click Cancel.
8. Choose Display > Colour model by attribute.
9. In the Attribute to colour by field, select gold_ok, click Scan, for the Ranges for colour selectiontype 0,15,1 and click Refresh.
10. Click Apply.



11. Display the legend on the Legend tab.

The data and model are displayed, as shown.



12. Choose Block Model > Close, and click Yes.

Task: Report tonnes and grade for an indicator kriged (IK) model

1. Choose Block model > Report.
2. Enter the information as shown on each of the five following forms, and click Apply.











The block model report opens in your default text editor.



Note: To see all of the steps performed in this task, run 2d_11g_ik_report.tcl. You need to click Apply on any forms presented.