directly. Programs are available for a Bendix computer to transform 

 red and green lane readings to latitude and longitude, and vice versa. 



The principal disadvantage of the Lorac system is that it is very 

 easy to lose count of the lanes. The phase meters, when once calibrated 

 and set, determine with high accuracy the user's position within a lane; 

 but, in order for the user to determine within which lane he is, he must 

 go to a known point and set the proper lane count on the meters. 

 Then, as the user moves through the area, a lane is added or subtracted 

 from the total each time the phase meters make a full revolution. 

 If a power failure, an electrical storm, or other interference occurs, 

 the lane count can be lost and can be recovered only by returning 

 to a known position and once again resetting the meters. This can be 

 very time consuming. In addition, the shore station equipment is 

 heavy and cumbersome. 



b. Loran (LOng RAnge Navigation) 



Several loran systems compose this family of pulsed, time 

 difference, hyperbolic systems. These are the Loran-A, Loran-B, and 

 Loran-C. 



(1) Loran-A 



This is a navigational system, rather than a survey 

 system, that uses frequencies in the vicinity of two megacycles and 

 has a maximum usable range of about 700 nautical miles. In a few 

 instances, Loran-A and Decca (another hyperbolic navigation system 

 similar to Loran-A) have been used in connection with Lorac or other 

 systems for lane-count purposes. Accuracies cannot be expected to 

 be much better than about a mile at ranges of 100 miles or more. 



(2) Loran-B 



This is a short range, high precision system having 

 frequencies in the vicinity of two megacycles and a range of about 

 300 nautical miles. It is still in the experimental stage. 



(3) Loran-C 



The Loran-C is a long range, high precision system that 

 uses phase comparison to refine the time difference measurement. 

 It has frequencies in the vicinity of 100 kilocycles and a range as 



XV- 9 



