Calculate Residuals
This command measures the accuracy of the strata grid model
based on the residual at each drillhole data point. The residual is
calculated by removing the data point and then comparing the grid
model calculation at the point with the actual value. Residuals for
any strata data value such as thickness, elevation or BTU can be
calculated using any modeling method including triangulation,
polynomial, Kriging, least squares and inverse distance.
Consider calculating residuals for thickness with five
drillholes. For each drillhole, the drillhole is temporarily
removed from the model and the thickness calculated at the
drillhole position. For example, one drillhole could have a
thickness of 5.0. When this drillhole is removed and the four
remaining drillhole using inverse distance calculate the thickness
at this point, the modeled value could be 5.25. The difference of
0.25 between the actual value 5.0 and the modeled value 5.25, is
the residual.
The first dialog to appear contains some settings on the
residual analysis.
- Ignore Zero Data
Values: This will ignore any values of 0 that are found in
the drillhole. They could be thickness, elevation or any quality
attributes. Sometimes they should not be ignored, depending on what
is being modeled.
- Use Report Formatter:
Turn this option on to see the report with the Report Formatter. If
it is off, then the standard report viewer is used.
- Calculate Histogram:
The Histogram is a statistical graph of the distribution of a
dataset. It shows the number of data samples within a series of
value ranges.
- Number of Histogram
Bins: The user can set the number of bins for the graph. For
example, if a dataset of sulfur has values from 1.0 to 4.0 and the
user asks for 3 bins, then the histogram will show the number of
samples between 1.0 to 2.0, between 2.0 to 3.0 and between 3.0 to
4.0.
- Mark Outliers: The Mark
Outliers option highlights data points that are more than 2
standard deviations from the data set average. This can be useful
for flagging possible problem data points.
- Mark Layer: This is the
layer of the circle mark drawn around the outlier drillholes.
- Mark Size: This is the
size of the mark, or circle drawn around the outlier
drillholes.
For triangulation and polynomial, the residual is not calculated
for some points because removing these points shrinks the
triangulation area and the point may fall outside the area. Also
you need more than three points to calculate residuals with
triangulation and polynomial methods.
Prompts
Select drillholes, channel samples
and strata polylines.
Select objects: Specify opposite corner: 269
found
Select
objects:
Reading drillhole 269
Choose modeling method [<Triangulation>/Inverse
dist/Kriging/Polynomial/LeastSq/ABOS]?
I
Use inverse distance to which power
[First/<Second>/Third/Other]?
Use elliptical inverse distance
[Yes/<No>]?
Calculating grid by inverse distances 4...
Try another modeling method (Yes/<No>)? N
Calculate BOTTOM ELEVATION residuals for strata 9
(<Yes>/No)? N
Pulldown Menu Location: StrataCalc
Keyboard Command: residuals