What is LORAN-C navigation? 



LORAN is an acronym for long range navigation. 

 And while it involves some relatively sophisticated 

 electronics, the principle of LORAN is based on sim- 

 ple trigonometry. Simply stated, a line of position is 

 obtained by measuring the difference in time it takes 

 to receive signals transmitted at synchronized inter- 

 vals from two onshore stations— a master and a 

 secondary or "slave" station. Location is further pin- 

 pointed or fixed by obtaining a second line of position 

 through the use of another slave station and the same 

 master station. Plotted on a chart, the point where 

 these two lines intersect is the position fix. 



Currently two types of LORAN are operating in 

 the United States. LORAN-A was originally 

 developed during World War II for military purposes 

 and was later adapted for civilian use. The more re- 

 cent LORAN-C was developed during the 1950s, also 

 for military purposes, and has been available for 

 commercial use along portions of the East Coast in- 

 cluding North Carolina since the early 1970s. Last 

 year C coverage was extended to the West Coast (both 

 U.S. and Canada) and the Gulf of Alaska. 



The primary differences between the two systems 

 involve the frequency of signal transmission, the 

 number of pulses each transmits and the way time 

 differences between signals are measured. Because 

 LORAN-C uses a much lower frequency (100 kHz) it 

 has a much broader range of coverage with a greater 

 degree of accuracy. 



The C system can pinpoint locations within a quar- 

 ter of a mile. And it enables mariners to "repeat" or 

 return to within 50 to 300 feet of these sites. By con- 

 trast, A is only accurate to within one to five miles. 

 Even this falls off dramatically at night when the 

 high frequency signals are often "drowned out" by 

 sky waves. 



The major users of LORAN are boat operators who 

 need a reliable, accurate navigational system for pin- 

 pointing their location and the location of bottom 

 obstructions and favorite fishing areas. Obviously 



Land 



Ocean 



not all mariners need LORAN for navigation. Along 

 inshore waters, radar and depth recorders are ade- 

 quate. A recent study by Sea Grant researchers at 

 Oregon State University indicates that only 30 per- 

 cent of the commercial fishing vessels along the East 

 Coast are equipped with LORAN, primarily LORAN- 

 A. The same study found that recreational boaters 

 are the largest single group of LORAN users. 



But it appears that the number of users is growing. 

 In light of the new 200-mile fishery zone and 

 heightened interest in offshore oil and mineral ex- 

 ploration, it is likely that it will continue to grow. 



