Methods of Observation 15 



energy of the ocean's emitted radiation. The airplane is flown below an 

 altitude of 1000 ft., and preliminary tests show that readings accurate to 

 1° F. are obtainable. The contrast in surface temperature across the Stream 

 is about 4° F. in late summer, 20° F. in late winter. It is estimated that 

 under favorable weather conditions for flying, the plane could make about 

 six zigzag crossings of the Stream from Cape Hatteras to longitude 65° W. 

 in a single 10 hr. flight. Such rapid surveys, which might be made twice 

 a month, are still in the planning stage. 



LORAN 



Loran is a form of radio navigation developed during the Second World 

 War by the Radiation Laboratory of the Massachusetts Institute of 

 Technology. Its coverage is not world-wide, but fortunately there is a 

 network of stations covering the central sector of the Gulf Stream System. 

 A h5rperbola of position is determined by accurately measuring (to 1 //sec.) 

 the difference in time between pulse signals sent at a constant rate from 

 two shore stations which emit in perfect synchronization. A Loran fix is 

 obtained by the intersection of several lines of position. Under the best 

 circumstances the fix is accurate to within 1/4 nautical mile, and fixes can 

 be made successively as often as every 10 min. This is a very great advance 

 over the method of celestial navigation, which is usually limited to 

 obtaining fixes at sunrise and sunset, and a latitude sight at noon. 



