Characterization of Visual Scanning Patterns in Air Traffic Control

Procedure 1

Counting the number of comparisons.

INPUT IGS

OUTPUT The number of comparisons made during the IGS

Step  1. Define 3 states as Scanned, Potential Comparison, and Comparison.

Step  2. If an aircraft is viewed for the first time, it is placed in Scanned.

Step  3. If an aircraft from Scanned is viewed for the second time, it is copied into Potential Comparison.

Step  4. If the next aircraft viewed is also from Scanned, it is copied into Potential Comparison as well. Otherwise, if a new aircraft is

viewed, it is placed in Scanned and the Potential Comparison state clears.

Step  5. If Potential Comparison is occupied with aircraft and one of those aircraft are viewed again, it is copied into Comparison.

Step  6. As long as aircraft in Potential Comparison continue to be viewed, they are copied into Comparison as one comparison.

Step  7. When an aircraft is viewed that is not in Potential Comparison, the comparison is complete, the number of comparisons

() is incremented, and the states Potential Comparison and Comparison are cleared. The aircraft that broke the comparison

is either new and belongs in Scanned or is already in Scanned and is copied into Potential Comparison to possibly begin the next

comparison.