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FAA Warns of GPS Outages This Month During Mysterious Tests On the West Coast (gizmodo.com)
Long-time Slashdot reader schwit1 shares a Gizmodo report: Starting today, it appears the U.S. military will be testing a device or devices that will potentially jam GPS signals for six hours each day. We say "appears" because officially the tests were announced by the FAA but are centered near the U.S. Navy's largest installation, China Lake, Californi -- home to the Navy's 1.1 million acre Naval Air Weapons Center in the Mojave Desert. And the Navy won't tell us much about what's going on. The FAA issued an advisory warning pilots on Saturday that global positioning systems (GPS) could be unreliable during six different days this month, primarily in the Southwestern United States. On June 7, 9, 21, 23, 28, and 30th the GPS interference testing(PDF) will be taking place between 9:30am and 3:30pm Pacific time. But if you're on the ground, you probably won't notice interference.
Maybe they are testing a way to jam gps for everyone else and it doesn't affect their receivers?
When a war between first world powers happens and the GPS satellites are destroyed on the first day, my sextant will continue to function. Good luck with your now useless GPS unit though.
Anyway, even in the 1960's experimental LORAN modes had accuracies under 6 meters, which is comparable to modern GPS. Money was not put in to develop this to wide deployment, but there was no major technical limitation. Some LORAN-C stations were still online as recently as 2 or 3 years ago, to serve as redundancy since GPS is easy to jam or destroy outright.
I agree. The US GPS, Navstar, is quite durable but it still requires a very extensive system to keep functional. It's also quite likely very expensive too but given it's capability the cost to benefit likely still falls in Navstar's favor over any ground based system.
The problem with a satellite navigation system is that if anything goes wrong that can affect many satellites, like the solar storm you mention, the means to repair or replace it is limited. We cannot simply fly up to a satellite and fix it. The only thing we can do is launch a replacement. If the satellite is truly dead then we'd lack the ability to re-orbit or de-orbit it and get it out of the way of the replacement satellite. It will be a hazard to subsequent satellites for 10,000 years. Launching satellites is limited to the number of spares on the ground and/or the rate in which they can be manufactured, as well as the rate in which they can be launched.
There are a number of ground based systems that augment or assist satellite navigation, WAAS is one that comes to mind, but they rely on satellite signals to operate. I assume it would be relatively trivial to allow these systems to operate autonomously but I've seen no effort to do so.
LORAN, VOR, and other ground based navigation aids are quite valuable in that being land based they can be repaired and replaced with much greater ease than anything in orbit. If there is an extended outage of satellite navigation then I'd expect ground based systems to get put into use relatively quickly but when talking about replacing an entire constellation of satellite navigation aids "relatively quickly" can still mean months, or even years. In the mean time we'd likely see many flights cancelled or put on longer routes because of reduced navigation capability. This would no doubt come at great expense and inconvenience. Had the US designed Navstar to integrate with ground based systems from the start then we'd never see this threat since the value of ground based navigation would be much more obvious and we'd not see systems like LORAN lose interest, and then funding, and then get destroyed.
Given the way that governments operate we'll see funding for ground based navigation fade to nothing until something happens to the satellites. At which point large sums of money will be allocated quickly with all the waste and corruption inherent with that panic. At which point, if we are lucky enough to have some smart people get paired up with some politically connected people, we just might get a very durable navigation system that integrates ground and satellite navigation seamlessly.
I doubt we'll be so lucky.
I am armed because I am free. I am free because I am armed.
Because likely the Navy is testing how to operate if someone ELSE is jamming GPS. The conspiracy theorists here on Slashdot are kinda missing the obvious.