eLoran, Eurofix & 9th Pulse
eLoran is a high power, low-frequency, accurate radionavigation system that delivers a 2-dimensional position, velocity, precise timing information and additional data to its users. The system operates at 100 kHz in a band reserved for radionavigation. For minimal navigation operation, a user needs to receive at least three stations, typically located hundreds of miles apart, that transmit pulses at precisely timed intervals. The excellent stability of the system yields repeatable accuracies of 20-50 meters and timing information accurate to within 50 ns from UTC.
The most fundamental enhancement of eLoran compared to the traditional Loran technology has been the addition of the ability of eLoran to broadcast data to the users. Technologies that implement this capability are EUROFIX and 9th pulse data broadcasting. Reelektronika, inventing the EUROFIX standards, has been at the heart of the development of these technologies and has implemented EUROFIX in its eLoran products. 9th pulse technology is currently implemented as well.
An eLoran receiver gets its location information by measuring the arrival times of the pulses of at least three eLoran stations. Using the measured timing values, the user is able to determine latitude and longitude of the receiver’s position, and its time with reference to universal time (UTC). With Loran the absolute accuracy of the lat/lon position is a function of effects to the signal passing over irregular terrain. These deviations from modelled propagation are known as Additional Secondary Factors, or ASFs. By measuring and mapping these ASFs, and adjusting the measured arrival times accordingly, the user’s position accuracy of 20 to 50 meters can be achieved. By using Differential eLoran techniques, the position accuracy can be further improved to the order of 10 meters. For further explanation of Differential eLoran, please refer to the Differential eLoran product specification.
Vulnerability of individual navigation products can be resolved with the integration of systems. eLoran is a self contained source of position, velocity and time. Its reliability can further be enhanced with the integration with satellite systems. Via the eLoran data channel, Loran can work as an augmentation similar to existing differential systems such as marine radiobeacons. Satellite systems’ excellent accuracy can be used to calibrate Loran to compensate for ASF’s. Accuracy, availability, integrity, continuity and coverage are all greatly improved compared to standalone satellite or Loran solutions.