LORAN Navigation Systems
LORAN is an acronymn for LOng Range Aide to Navigation. LORAN navigation systems used radio wave transmissions to obtain geographic position information. As the technology evolved, several versions of LORAN were implemented. LORAN-A was the first widely used system. Eventually LORAN - C was developed and implemented in the United States, Canada, and other nations throughout the world.
To understand how LORAN technology works, A good analogy is to imagine watching ripples on a pond as you drop multiple stones in the water. The rings that eminate outward from each dropped stone travel at predictable speeds and cross each other at given intersections. Similarly, radio waves travel and intersect over water in a predictable manner.
Exceptions occur when radio waves travel over land or other obstacles. These errors are controlled using algorithms called additional secondary factors or ASF's. Once the errors are resolved, the time delays (TD's) can be accurately plotted on a chart.
Modern GPS receivers are equipped with plotters, maps, and endless menu options. Early LORAN- C units had no such features. Usually a screen gave a variety of data such as course, heading, distance to go, navigational error, etc. Rather than showing a fix on a plotter or chart, a page showed a pair of numbers, called time delays (TD's). Position is plotted by finding the approximate TD's on a special chart and locating the intersection. LORAN - C receivers.
LORAN units typically operated on 12 volts and consisted of 3 components. The control head contained a processor, keypad and display. The coupler contained much of the signal processing components. The antenna sat atop the coupler. LORAN-C antennas are bulky, usually 8 feet in length. Most LORAN-C units provided NMEA data outputs, which allowed units to share navigational data with other electronics.