NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Dependence on GPS
From: Frank Reed
Date: 2009 Oct 30, 16:01 -0700
From: Frank Reed
Date: 2009 Oct 30, 16:01 -0700
Hi John, you wrote: "It wasn't an issue of the conditions of the moment, but rather what I suspect was the build-up of crud on the receiver over time that led to a failure. After two failures, I threw in the towel on the devices. " There's no doubt that GPS receivers of all stripes do fail. And a big issue here is expense. If they fail with high-enough frequency, then we are thrown back on traditional navigation just as a matter of economic necessity. All technology fails. Chronometers used to fail quite regularly, and in a way that is far more dangerous than the failure of GPS (a GPS receiver will almost always fail completely with an obvious indication that it is dead, while a chronometer will degrade to dangerous performance without any visible indication). But that doesn't mean we should avoid chronometers, nor does it mean you should abandon GPS. The trick is to use it in such a way that limits failures. Those dry pouches work, for example. Also, by far your best defense is to carry a spare. The spare should be a different make and model and stored in a different way from your main receiver to avoid the trap of identical failure modes. It should also be stored in a small metal case to serve as a Faraday cage. Now of course this is NavList, so we're all about traditional methods of navigation, but if you're out there risking life and limb, I personally would never suggest to anyone that they use anything but the best available technology, and that they should back that up by the best available technology. There's no reason to risk your life or anyone else's for the sake of an enthusiasm for traditional navigation. And other people's lives *are* involved whether we like it or not. If you go missing for some extended period of time, unless you're heading out on the water without telling a soul, the Coast Guard will eventually come looking for you. The lives of those searchers are then at risk (see yesterday's news from California regarding a Coast Guard C-130). So far we're talking about the failure of GPS receivers. They do fail, and you can be prepared for that failure by carrying a spare GPS receiver. Peter tells us that he has had multiple GPS receivers all fail all at once. That kind of astronomically improbable bad luck seems to strike certain people, but it's not the sort of thing that could be considered normal. Only an electical shock could kill multiple receivers at once under normal rules of "luck", and to defend against that possibility the solution is to keep your spare GPS in a metal box to serve as a Faraday cage (does anyone sell this as a standard item?). But beyond receiver failure, there's a much less likely yet still important risk that the GPS signal itself might fail. There are cases where you might have a somewhat degraded position accuracy if one or more satellites fails, but those are temporary conditions and apparently very rare. Of greater concern is the prospect that GPS signals might be jammed over some region, perhaps dozens of miles in extent, for a military or criminal purpose. I'm not talking about a direct military assault on the satellites or the ground stations themselves. If that happens, we're looking at war and we'll have bigger things to worry about. Instead consider a scenario where someone holds a major port hostage by planting dozens of concealed remote-controlled GPS jammers and then issues a demand: pay up and you get your GPS signals back. Tracking down jammers is not easy... good luck to whoever faces this scenario when it finally happens. Further, as governments attempt to use GPS for enforcement (tagging criminals on probation, e.g. or tagging ordinary vehicles for road taxes), there will be an inevitable rise in the use of jammers and also GPS signal spoofers. The latter are even more worrisome since they would yield erroneous positions in receivers that appear to be functioning correctly. There are always things to worry about, and for GPS and other such signals, the future may be worse than the present. The current issue of "GPS World," in which long-time NavList member Richard Langley has a monthly column, has a brief and interesting article about GPS jammers and spoofers. That's what got me thinking about criminal scenarios as described above. -FER --~--~---------~--~----~------------~-------~--~----~ NavList message boards: www.fer3.com/arc Or post by email to: NavList@fer3.com To , email NavList+@fer3.com -~----------~----~----~----~------~----~------~--~---