1 1 Excellent (within 3 metres)
2 2 Good (within 10 metres)
3 3 Fair (within 20 metres)
4 4 Poor (more than 20 metres)
5 5 Excellent (within 3 feet)
6 6 Good (within 10 feet)
7 7 Fair (within 20 feet)
8 8 Poor (more than 20 feet)
15 15 Missing value
