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Array:
The Array module used to manipulate mathematically one, two, or a series of 2D or 3D grid files. Depending
on the options
selected, operations include addition, subtraction, multiplication, division, averaging, minimum, maximum,
probability value within a range, reclassification, and basic statistics. These are basic grid tools used in
Geographical Information Systems (GIS). This tool can be useful for data preparation, or for data and result
analysis.
For example, by reclassifying a contaminant plume map and a geologic uncertainty map, it is possible
to optimize future sampling to collect data in areas of greatest risk and uncertainty. Here, two "cost"
grids are multiplied together:
The red areas represent areas where 1) the least is know about the geology, and 2) where the
geology is most conducive to contaminant flow. The blue areas represent areas of 1) where the
geology is believe to be well describe, and 2) nonconducive to contaminant flow.
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The red areas represent areas near the EPA standard for this contaminant. The goal here is to define
the boundary of the legally contaminated zone. The blue areas represent areas which are 1) unlikely
to have any contamination, or are 2) highly contaminated.
We know the highly contaminated areas
will need to be remediated, and are more interested defining the boundary of actual contamination.
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Given the two maps above, and assuming they are of equal importance (if this isn't true, array
can use weights), these maps can be multiplied together.
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The results of combining the above map identifies area of both high geologic and contaminant
uncertainty or risk. By concentrating future exploration in the red and green areas, the risks
associated with the assumptions defined here could be minimized.
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