ANALYSIS OF ERRORS IN RADAR 65 
Set Freq. Band Accuracy Required 
AN/CPS-+4 Ss 1,000 ft in absolute altitude and 
500 ft in relative altitude at 45 
miles range, preferably 90 miles. 
AN/CPS-6 s 1,000 ft in absolute altitude and 
500 ft in relative altitude at 75 
miles range, preferably 100 miles. 
AN/TPS-10 x 1,500 ft in absolute altitude and 
500 ft in relative altitude at 50 
miles range. 
TROPICAL ATMOSPHERE ORY AIR ABOVE 
TROPICAL ATMOSPHERE 
STANDARD ATMOSPH 
ERROR IN ALTITUDE IN 10° FT 
WW 
V. 
RANGE IN MILES 
Thus with the % earth radius correction the error 
remains under 1,000 ft at 75 miles. However, these 
atmospheric conditions represent normal conditions 
so that in specific meteorological situations the error 
may exceed 1,000 ft in 75 miles especially in the 
trade wind regions. 
Since the maximum error occurs at a true angle 
of 0°, these errors in absolute altitude for a range of 
75 miles are tabulated for true angles of 0° to 3°. 
APPARENT ALTITUDE 
TRUE ALTITUDE 
HORIZON PLANE 
TRUE EARTH 
TROPICAL ATMOSPHERE DRY AIR, ABOVE: 
ieee 
TROPICAL ATMOSPHERE Z| 
i 75 100 
RANGE IN MILES 
Ficure 1. Maximum errors in absolute altitude due to atmospheric refraction. A. True earth radius. B. 4/3 earth 
radius. Target assumed to be at true angle of zero degrees. 
ABSOLUTE ALTITUDE 
Figure 1A indicates the errors in absolute altitude 
for different air masses on the assumption that the 
target is at a true angle of zero degrees. Thus at a 
range of 75 miles the error in elevation is 940 ft in 
Tasxe 2. Errors in absolute altitude for early warning 
heightfinding. Range 75 miles. 
True Angle of sight.(degrees) Errors in altitude (feet) 
angle Standard Tropical Standard ‘Tropical 
0 0.14 0.20 941 1,412 
1 1.12 1.17 823 1,332 
2 2.10 2.14 705 970 
3 3.09 3.12 626 845 
a standard atmosphere and 1,880 ft in a tropical 
atmosphere with dry air above. Figure 1B depicts 
‘the errors on the assumption that the standard 
atmosphere correction (% earth radius) is applied. 
ERROR IN ALTITUDE IN 10° FEET 
50 75 
RANGE IN MILES 
Figure 2. Maximum errors in absolute altitude due to 
surface ducts with standard atmosphere above. 
