Navigational errors make a big difference if you are flying near hostiles. And nextnav.com says GPS is easy to spoof, because the signal is unencrypted.
I remember trying to follow directions to a party in Gex, and not recognizing an exit from a roundabout as a real exit (it was night, and the road was tiny). That exit miscount, followed by precise adherence to the subsequent turns, ended up with me having to back the rental car up out of a cow path in the middle of nowhere, France. Cell phones were not a thing back then. Paper maps are your friend.
4 comments:
One son had a similar experience after visiting a friend in Wisconsin (he started in Texas) and trying to get back to NH via the Upper Peninsula of Michigan. Something went wrong in the national forest there, and he was skirting the side of a lake in the middle of the night when the dirt road just...ended. And also, when the family was at Grand Canyon 11 years ago, someone's mapping app took us around the back of a mountain, into roads not maintained by, hmm, anyone, apparently, rather than around the front.
But I will have to say I had far more problems with maps. My brother likes to say "Good stories come from bad decisions. I have lots of good stories."
My wife and eldest daughter were following the map along the edge of a forest in northern Wisconsin, and discovered that what the map thought was a road was really a sand track, suitable for getting minivans stuck in.
Sounds like the same road!
Inertial navigation systems drift over time...the length of time they can be relied upon varies with the design of the system. The very expensive systems used on nucleaer submarines are probably at the high end. I don't know how long the typical inertial system on an airliner is good for without needing a reset...probably longer for planes intended for transoceanic serve.
One possible approach would be to have one inertial system that is frequently reset by GPS data and another one which is not, and display to the flight crew the amount of divergence between the two. If it gets too large, something weird is going on.
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