Originally Posted by
zed3
So, if the GPS goes down, for example due to conflict or jamming, there is no back up. At least VOR/DME is terrestrial and under control. This is something I've been thinking about for a few years. Must be financial and budget balancing. Very misjudged in my opinion.
Well, there is GPS, Galileo, Baidu and GLONASS. As far as i am aware at least GPS and Galileo are compatible with each other for "normal" precision. However, most airliner do only use GPS so far which is of course a result of the extremely long development cycles. Most of us carry a smartphone around, and they can use all four systems and have been able to do so for the last 5 years already. And of course our workplaces (airplanes) usually carry 2 or 3 inertial systems around, even if we lose both GPS and nav aid updating that allows quite a bit of navigation precision for a significant time.
That said, as far as i know VOR and NDBs are scheduled to be decommissioned, DME on the other hand is not, as it is a pretty nifty backup system that is both ground based and more precise than VOR or NDBs.