Extensive field and laboratory tests have been performed by the USC 

 & GS to determine the EPI system's accuracy and consistency. Table V-1 lists 

 these data as a percentage of observations that come within the fraction of micro- 

 second indicated. Accurately measured distances of 45, 90, 110, and 267 

 nautical miles were used . A total of 267 sets of observations were made. These 

 tests also indicate there is little correction required to compensate for signal 

 strength or distance between the ship and ground stations . 





TABLE V-1 





FIELD TEST DATA FOR EPI 





% Observations Within Specified Limits 



Limits of Error 



Field Tests Laboratory Tests 



± Microseconds 



267 Observations 21 Sets of Observations 



0.1 (15 meters) 



35 26 



0.2 (30 meters) 



53 53 



0.3 (45 meters) 



72 71 



0.4 (60 meters) 



83 82 



4. SUMMARY 



a . Type of System 



(1) Pulsed phase-difference circular plot. 



(2) Number of stations required: 2 shore stations, 1 shipboard 

 station . 



(3) Length of base line: 50-250 miles. 



(4) Operators required: at ground stations and on shipboard. 



(5) Transmitter pulse width: 60 microseconds. 



(6) Transmitter pulse repetition rate: 41-2/3 per second. 



(7) Shipboard transmitter frequency: 1.85 mc. 



(8) Shore station transmitter frequency: 1 . 85 mc . 



(9) Shipboard and ground station peak pulse power: 10-18 kw. 



115 



artbur ai.llittlejnr. 



