3. ACCURACY 



Extensive sea and land tests indicate that the Omega system's ac- 

 curacy is better during the day than during the night or during transition periods . 

 A statistical analysis of long-term tests at three of the fixed stations indicates 

 a navigational accuracy of 0.5 and 0.9 nautical mile (circular probable error) 

 in the daylight and the nighttime hours, respectively. Relative accuracy of 

 vessels for station keeping should be of the order of 0.25 mile. At present, 

 errors during transition periods (day/night and night/day) are less than 2 miles . 

 Statistical studies at NEL indicate that inherently, transition period accuracies 

 are capable of being intermediate between day and night values. To realize 

 this capability, more numerous corrections computed by more elaborate methods 

 may be required . 



A recent analysis''*/ indicates that the Omega system should be capa- 

 ble of an operational fix accuracy of less than 6 nautical miles. More recent 

 experimental data and improvements in equipment indicate this figure is con- 

 servative . 



With present base lines NEL reports the operating range consistently 

 reaches 6000 nautical miles. Some estimates indicate the present system can- 

 not be made operational for world-wide use until the late 1960's or early 1970's. 

 It must first be qualified by test and accepted for use by Federal authorities . 

 Also the establishment of suitable transmitter sites on foreign soil requires 

 considerable time and preparation. A recent report'^' describes the siting 

 problem in some detail. 



4. SUMMARY 



a . Type of System 



(1) Pulsed phase-difference hyperbolic plot 



(2) Base line length: approximately 5000 miles 



(3) Pulse duration: 1 sec (adjustable cw synchronized) 



(4) Pulse repetition rate: 5 sec (adjustable up to 10 sec) 



(5) Transmitter power: 1000 kw 



(6) Radiated power: 2-3 kw 



83 



arthur Zn.lltttlcilnr. 



