It's always nice to see an old tech stage a comeback and this time it's happening around the coasts of Europe, with nine low-frequency radio transmitters substituting for GPS' satellite-based system. eLoran's radiowave-based system is stronger than satellite signals and less jammable, based on the Loran system that was previously used for shipping navigation by both the British and US navy over 50 years ago. But despite its age, the tech has proven remarkable hardy against unwanted interference. In trials conducted by the General Lighthouse Authorities of UK and Ireland, a 1.5W radio jammer was able to knock out GPS signals over a range of 30 kilometers. However, to do the same to the Loran system, you'd need a 40ft tower -- and around 25kW of juice to power it.
The basics behind Loran and GPS are largely the same, with devices measuring the time it takes for a signal to travel between a transmitter and your receiver. Loran requires three singles, with locations then calculated through "trilateration". More signal input subsequently equals a more secure position read-out, with the elderly base system offering initial location accuracy to around 100 meters. However, the updated eLoran signal (currently only being broadcast on the east coast of the UK, around Dover) will narrow that down to the nearest 10 meters. The GPS back-up will be gradually rolled out across the entire British coastline.