A cumulative threat risk value for each of the grid cells is calculated, and {HEAD ~ an allowable threat risk} per {TAIL ~ grid cell} is established based on a rule set 
per
A cumulative threat risk value for each of the grid cells is calculated , and { HEAD ~ an allowable threat risk } per { TAIL ~ grid cell } is established based on a rule set
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH