pin VACLASSIEI IFIED B; Accuracy of Data Collected by Aircraft In the past there has been considerable criticism on the advis- ability of using extrapolated airplane data for radiological monitoring. Howaver, in this study, it is possible for the reader to judge for hinself the accuracy and the usefulness of the radiological data collected by aircraft, since the air resdings and the ground readings are individually plotted for easy comparison. <A careful study of the airplane eetpney,diate i data shows that it is not possible to obtain accurate indication of the centamination on the zround if the contaminated area is less than five aquare miles. is useful, However, for large area contamination, the airplane data This means that there need not be any extreme accuracy re- quired in the navigation of aircraft, sin: errors of one or two atles could be tolerated. In some instances the airplane data is more useful than the ground data in delineating the overall radioactive fall-out | picturs, This was demonstrated semewhat dramatically during the first shot cf U/K Test Operation, During this particular tast, St. George, Utah received an infinity maximm dose of 0.5 roentgens in the center ef the city (see Figure 5). However, the airplane reading indicated that the contamination at St. George was 3.3 roentgens, disconcerting at the tims. This was quite It developed later that just at the northern cutakirts of the city there was a smal] radioactive zone of 6 roentgens ae and further north there was a five mile wide layer with an average infin~ ity dose of 3 reentgens, what the airplane had dene was to average the We ore + total and give a 3.3 reentgen reading because it was flying at an alti- aw tude of 500 ft, and therefore the instmment in the plane ceuld "see" a y UC C3- UNCLASSIFIED a