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However, often your inputted data will not be in the right format for a direct input. There are
several programs around which can take drill-hole data and turn it into a block
model. Gemcom is one such program. These programs can output this block model to
a text file, so that other programs can read it. An example of such a text file is can be seen here. This shows the typical format for such a text output file. There are four
columns. Each row lists the data for a single block in the block model. The
first three numbers shows the location of the block (in (i,j,k) format), and the
fourth number is the numerical value of that block. When you open this file in Excel, it looks like this:
This is how
Excel interprets a text file. Each data point gets distributed to a cell. Before
a pit limit can be determined, this data needs to be converted into the format
seen previously, where each cell represents a block. To convert this data into a format which UPL can use for determination of
the ultimate pit limit, you need to go to the UPL menu, and select ‘Data
Transform’. Checking first in the ‘Transform options…’ menu that
‘I-J-K mode’ has been selected. This transforms the data into the respective
rows, columns and sheets, as required. The results from the transformation subroutine can be seen here:
This transformation sequence works in all three dimensions, transforming
all data in the ijk format into the block model, where columns are the x
dimension, rows the y, sheets the z, and cells are the blocks. It also resizes
the blocks to the given dimensions. The primary
limitation of the transform algorithm is the input data. Excel can only handle
65,536 rows in any one spreadsheet. When a text file in opened, then, Excel
cannot open it if it contains more than 65,536 rows. Because each rows
represents a block in the block model, this would place the ultimate number of
blocks which can be input at any one time to 65,536. If the block model contains more than 65,536 blocks, you have two options. You can either reblock the block model (reblocking is when a block model is reduced in the number of blocks that it contains), or run multiple inputs. The block
model can be divided up into groups of z-slices, then each of these groups are
imported separately. Once each of the groups has been transformed, it is an easy
task to group sheets from multiple outputs into one workbook, though UPL does
not currently have this capability. Care needs to be taken however, in keeping
the sheets in the correct order. The data transformation submenu has two primary options, which can be selected from the UPL menu. The options cater for different input data formats. The Data Translation Options menu can be seen below:
The first
option asks you to select between the ‘Economic Value Format’ and the
‘Grade Value Format’ for the Block data. This refers to the fourth column on
the input data. A file that uses the grade value format may be converted into
the economic value format using this option There are
two primary ways of assigning block data. One is to output the actual block
value. Another is to output the grade value. The grade value is more commonly
used, since the grade in the orebody does not change, yet the block value
changes constantly. To calculate
the amount of ore, and the amount of metal in the block, the block dimensions
must be known. These block dimensions can be entered in the lower part of the
‘Block Data’ tab. To further
calculate the block economic value, the economic and geological data for the
block needs to be entered. This is done via the ‘Economic Data’ tab in the
Translation Options screen:
All the necessary data to calculate the economic block value is inputted
from the screens shown above. Once this data is in place, running the
transformation program will produce an output that has economic block values,
instead of the block grade values. It is important to produce an output which
has economic block values, since the ultimate pit limit is a calculation based
upon the pit that has the highest economic value. The output from calculation of the economic block value can be seen
below:
The block
values are very different from those seen previously, since they have been
converted from a ‘grade block value’ to an ‘economic block value’. Also,
the block size is not square, since, as can be seen in the Translation Options
menu, the block dimensions are not square. The next
option on the ‘Block Data’ tab deals with the format of the first three
numbers in the data file. Instead of using i-j-k values to specify the location
of the block, the model may use numbers based on their relative locations. In
this, the location of the block is defined as being some distance away from a
given datum. For instance, consider the data file seen here. Clearly, this will not produce a desired output when UPL uses i-j-k
formatting, since blocks that are meant to be next to each other (ie, 60, 75 in
the x-direction) will instead end up some 15 blocks apart. In order to produced
a correct output, more data needs to be input into the ‘model data’ tab:
The minimum
and maximum for the block model needs to be entered into the sheet. The program
then, with the aid of the block size, calculates the total number of blocks in
the model, and assigns the data to these blocks. An advantage
in using the x-y-z model system is that you can specify a region which may be
smaller than the block model for which they have data for. In this case, all the
data which lies outside of the your specified region will be ignored. Using the data inputted into the option menus, the output will be identical to the I-J-K file output, as can be seen below:
Once
all data has been translated into this format, it is ready for UPL to determine
the ultimate pit limit.
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