It’s for estimating the iniatial fallout area after a nuclear detonation, determining expected fallout arrival time, and determining who needs to evacuate and who should shelter in place. It is used as a map overlay
The inputs to the plotter come a series of other nomograms that take into account the windspeeds and directions at vatious altitudes. The data is distributed down in the form of an NBC-3 report.
For personnel who shelter in place you can use that “whizz wheel” shown in the picture to determine the best time to evacuate.
