Consol and the new Canadian microwave position fixing system; and 

 composite systems, such as the latest Raydist (a combination of both 

 hyperbolic and ranging systems). Each of these systems is discussed 

 briefly. 



2. Hyperbolic systems 



a. Lorac (LOng Range AC curacy) 



The Lorac, built by Seiscor, a division of Seismograph 

 Service Corporation, is a continuous wave, phase comparison, hyper- 

 bolic system that uses three shore stations and permits an unlimited 

 number of users. It uses frequencies in the vicinity of two megacycles. 

 The useful range is about 200 nautical miles, and accuracies range 

 from about 15 feet on the base line to about 400 feet at the outer limits 

 of the usable area. 



The shore equipment consists of four transmitters and two receivers 

 and establishes the hyperbolic lattice by using two pairs of frequencies 

 with an audio n beat n frequency of 315 cycles between the two frequencies 

 of the red pair and 135 cycles between the frequencies of the green pair. 

 The red, center, and green stations should be established at about 60 

 to 120 miles apart, with the angle between the two base lines preferably 

 less than 135° and preferably with the triad concave toward the area of 

 interest. A position is read from the phase meters of the shipboard 

 receiver in the red and green "lanes. n A lane is a half-wave length 

 which is roughly 230 feet wide (depending upon the frequency being 

 used) on the base line. 



As the hyperbolic lines of position depart from the base line they 

 spread apart, so that as the outer limits of the service area are 

 approached, a lane has expanded to some 1,380 feet in width. In other 

 words, the accuracy degenerates with distance from the shore stations: 

 a phase reading error of 0.01 lane equals about a 2 1/2-foot error on 

 the base line but becomes about a 14-foot error near the limits of 

 the service area. The accuracy is also dependent upon the angles of 

 intersection of the lines of position; as long as these are between 15° 

 and 165°, the system is adequate. It is highly desirable that there 

 be a minimum of overland transmission between the stations of a 

 triad and between the stations and the service area, because such 

 transmission seriously degrades the accuracy and effectiveness of the 

 system. 



The hyperbolic lattice can be computed and laid out on plotting 

 sheets so that the lane readings from the phase meters may be plotted 



XV- 8 



