14-8] 



DOPPLER NAVIGATION SYSTEM PERFORMANCE DATA 



755 



14-8 DOPPLER NAVIGATION SYSTEM PERFORMANCE 

 DATA 



One doppler navigation system for which a large number of actual test 

 data exist is the AN/APN-66, probably the first of all doppler navigation 

 systems. A histogram of one set of test flights by Wright Air Development 

 Center, Dayton, Ohio, of the AN/APN-66(XA-2) Doppler Navigation 

 System over land is shown in Fig. 14-12. From this histogram the so-called 



12 



10 





59 Runs 

 Land 

 X= 0.51% 



m 



n 



n 



0.6 1.2 1.6 2.0 



POSITION ERROR 

 (% DISTANCE traveled) 



2.4 



Fig. 14-12 Flight Test Histogram AN/APN-66 (XA-2). After R. M. Gustin, 



"Flight Test Results of Navigation Set, Radar AN/APN-66 and AN/APN-82," 



WADC Tech. Note 55-746. 



most probable position error or the mode of the curve, is found to be 0.42 per 

 cent and the mean error is 0.51 per cent of distance traveled. When these 

 data are processed statistically, a fitted probability distribution curve can 

 be drawn, and this is shown on Fig. 14-13. This is a plot of the cumulative 

 probability distribution of the circular position error of the AN/APN- 

 66(XA-2). From this curve it is found that the "probable error" (50 per 

 cent probability) is 0.52 per cent of distance traveled, and the "maximum 

 error" (95 per cent probability) is 1.2 per cent of distance traveled, giving 

 a ratio of maximum to probable error of 2.31. Thus the data on the 

 AN/APN-66(XA-2) closely fit the case oi gtIctr = 2, which was cited as a 

 typical example earlier. 



