GPS is too easy to block or spoof. Same for GLOSNASS (the Russian version). And probably – though this article doesn’t say – the EU version of satellite nav, Galileo. Radio navigation set to make global return as GPS backup, because cyber | Ars Technica
Over the past few years, the US Coast Guard has reported multiple episodes of GPS jamming at non-US ports, including an incident reported to the Coast Guard’s Navigation Center this June that occurred on the Black Sea. South Korea has claimed on several occasions that North Korea has jammed GPS near the border, interfering with aircraft and fishing fleet navigation. And in the event of a war, it’s possible that an adversary could take out GPS satellites with anti-satellite weapons or some sort of cyber-attack on a satellite network.
The US Navy shut down GPS over a section of ocean just off the Eastern Seaboard several years back – maybe as many as 10 or so. And I have heard reports from friends that the system isn’t active around Washington DC, which wouldn’t surprise me, but I don’t know if that is true.
LORAN only gave you a position accurate to about 20 meters or so, and then you were supposed to rely on the Mark 1 eyeball to determine your exact position. If there was a widespread hack or failure of the GPS system, I wonder how all these self-driving cars and self-flying package- delivery drones would handle it.
And while eLoran only works in two dimensions (it doesn’t provide altitude data) and only works regionally (with a range of 800 miles), it has one major advantage over GPS: its powerful low-frequency signals are far less susceptible to jamming or spoofing. The signal from eLoran beacons is 1.3 million times stronger than GPS signals. A 2006 MITRE study found that attempts to jam or spoof eLoran would be highly unlikely to work.
Both Obama and Bush pushed for the roll out of the new LORAN (eLORAN) but it was never funded by Congress.