When it comes to global, ground-base positioning systems, there are only two real options: Differential GPS and LORAN. Differential GPS (DGPS) is already used extensively in maritime and aeronautical settings, to provide more accurate positioning data (down to a few centimeters) for ships and planes. I won’t get into the technical details of DGPS, but it basically consists of a few ground-based antennas that work together to get a really accurate GPS fix, and then broadcast their findings to any nearby GPS receivers. This system works very well, but ultimately is still vulnerable to GPS jamming (or, say, GPS satellites being knocked out of action by a giant solar flare).
LORAN (LOng RAnge Navigation) is a different beast entirely. Originally developed during World War II, LORAN consisted of low-frequency (3-8MHz) transmitters that, using hyperbolic navigation, provided a modicum of navigational guidance for Allied aircraft and ships. Despite the low frequency signals bouncing off the ionosphere, the maximum range was only a few hundred miles — and due to the difficulty of processing (more like interpreting) hyperbolic signals, accuracy wasn’t that great either.
LORAN went through a few iterations (A, B, and C), and as transistors and digital computers became commonplace in the 1970s, the system actually gained a decent level of accuracy. By the 1990s, though, with GPS and other global navigation satellite systems (GNSS) coming online, LORAN usage dropped off rapidly. Many LORAN systems have now been shut down, in favor of cheaper and more accurate GPS and DGPS.
In recent years, though, as we’ve grown scarily dependent on GPS, some countries have started looking at LORAN with fresh and renewed interest. LORAN’s use of low-frequency, very-high-power radio waves (the base stations usually transmit at thousands of kilowatts) means that it’s very hard to jam a LORAN signal. In general, LORAN’s infrastructure and mode of operation is so different from GPS that it makes for a very safe fallback. When you have massive cargo ships loaded up with millions of dollars of cargo, or military aircraft that are en route to bomb a target, relying on a weak signal from outer space seems somewhat foolhardy. Having a backup in the form of LORAN is really sensible.
A bright, precisely positioned future
This week, the UK turned on seven new eLORAN stations along its east coast — the first major new deployment of LORAN in years, and a direct response from the UK government to the threat of GPS jamming. Over in South Korea, home of some of the world’s busiest ports, eLORAN is being installed to mitigate against North Korean GPS jamming — the DPRK jammed South Korea’s GPS for 16 days back in 2012, and indeed radio jamming of all varieties is pretty common over there, especially around the DMZ.
For now, the UK and Korean systems are purely for shipping, but in the future they could be used on land, augmenting and improving upon GPS. Another advantage of LORAN is that its low-frequency, high-power signals can be picked up indoors, at street level in high-rise cities, or even underground — potentially a huge deal as far as indoor positioning systems (IPS) are concerned, and also significant as urban populations increase.
It remains to be seen if other countries will join the LORAN revival — but I have a feeling they will. If GPS has taught us anything, it’s that precise positioning is extremely valuable — in terms of navigation, but also for leisure, safety, business, and more. As mobile and wearable computing grows ever more ubiquitous, positional data will underpin almost every aspect of communication, commerce, and the fabric of society itself. There’s just no way that we’ll rely on a constellation of satellites that are more than 10,000 miles away — we will build out a global ground-based navigation system, it’s just a matter of when.