Recall sample file
This function allows you to recall a string file containing interval or point sample grades so grade estimates can be made.
To run this function: Choose Design > Grade control > Open sample file, or...
The string file must meet one of the following criteria to be acceptable for use by the grade estimation methods:
- The string file must contain points which represent elevation composites of all the samples within a nominated elevation range for one or more drill holes.
- Each point represents a drill hole.
- The description fields must contain the grade values.
- The string file must contain one or more segments where each segment represent the path of a drill hole or channel projected onto a vertical or plan section.
- grades are stored in the description field of the point which represents the bottom of the sample.
Use the composite by elevation function to create a string file like this.
Below is a portion of a string file created by the composite by elevation function.
Use the Extract Sections For Calculation to extract plans for calculation functions to create a string file like this.
Below is a portion of a string file created by one of these functions. Note that each string has more than one point and successive pairs of points define the length of each sample and the sample
To make the grade estimates you must use a segment which represents the area within which the grade estimate is required. You may recall a string file which contains previously defined strings for this purpose or you may use the DIGITISER functions and EDIT functions to create or modify segments as required.
Define the sample string file to be used
Enter the Location and ID number of the string file which contains the sample assays which are to be used for grade estimation.
Assay Field
Enter the number of the description field, i.e. D1, D2, etc., which contains the sample assays.
Thickness
Enter the nominal thickness of the bench or section for which the grade estimates are to be made. This results in the area of the segment within which the grade estimate is to be made being multiplied by the thickness to produce a volume estimate.
S.G.
Enter an estimate of the specific gravity to calculate an estimate of the mass of the material delineated by the polygon. The mass is simply calculated by:
Mass = segment area * thickness * SG
(P)oint or (I)nterval samples
You must define whether the sample string file which is being used represents point samples, i.e. elevation composites, or interval samples. Enter "P" for point samples or "I" for interval samples.
The value entered here defines how the samples will be drawn. Point samples will be drawn with a marker, a label and a grade value. Interval samples will be drawn as a line with tick marks to indicate the location of samples along the drill hole or channel trace. The sample grade is drawn perpendicular to the line representing the drill hole trace.
Dilute blank or negative samples (Y/N)
In certain conditions, samples may be missing from the string files containing the sample values. The missing samples are represented by either assay values which are less than zero or blanks in the description field that contains the assay values.
There are two different methods available to handle missing samples in the calculation process:
- Y, the sample will take on an assumed value of 0 (zero). This has the effect of reducing or diluting the final average grade.
- N, the sample will be ignored completely and it will have no effect on the final result.
Define the description fields for the results
Grade, Volume, S.G., Mass, Area and Thickness
The results of the grade estimation are written to various description fields of the segment for which the grade is estimated. You must enter the number of the description field for each of the results which are produced.
The specified string file is recalled and the samples are drawn in the appropriate style. At this point you are ready to use the grade estimation functions.
Note: For point sample data you may wish to use the Classify Strings function to sort the points into different strings using the grade value. This may be particularly useful if different colours are used for different strings.