of dosage, the accepted level has been set at three feet above the ground. The relationship between the intensity measured at the air- craft and the three foot intensity is proportional to (over an altitude range from 200 - 1000 ft.)s I, * Ip= (See Figure 7) (1) I, * radiation intensity in airoraft I, 2 radiation intensity at ground level u, = Mnear absorption coefficient of air (2¢74) X = altitude (ft) Then Ip = Ty (2) EX And ¢ -i_ Ee (3) where fa = altitude correction factor from (2) & (3), Ip = f, x I, (4) and Log 1, = log f, + log I, (5) from (3) f, =L - Etux (6) log f, = ux or log f, =X Because the detector output is designed to provide a logarithmic response, it is only necessary to add the log fe electrically to ob= tain log Tee Also — log f, is directly proportional to altitude (equation 6) and thus may be derived from a radio altimeter. It is not possible to maintain an aircraft in level flight and the changes of # 50 feet which normally occur will create large changes in the radiation reading, - 13 <- Thus it is essential to