80 



60* 

 < 



40 

 20 

 00 

 80 

 60 

 40 

 20 



00 

 0000 



• ••••••• 



.f 





0400 



0800 



1200 



TIME (GMT) 



1600 



2000 



2400 



Figure 3. Typical 10.2-kc/s Omega phase difference. Half-hourly measurements on 

 Criggion-Summit in-port at Chaguaramas, Trinidad, 21-24 Dec 63. 



2300 and 0800Z while all are sunlit between 1130 and 1600Z. 

 The figure shows the usual features of the Omega phase 

 difference, namely, constant (or "flat") at night with a slow 

 change (or "curvature") during the day. 



Because phase differences tend to be constant at 

 night, a single average nighttime phase difference may be 

 meaningfully computed for each of the site-LOP's. The 

 average values observed, combined with appropriate lane 

 assignments, may then be compared with theoretical compu- 

 tations. Such a comparison is shown in table 1 where the 

 theoretical computations were based on the determination of 

 phase coefficients made early in 1965,^ The last column is 



12 



