It's easy to forget that airliners often don't have a moving map GPS so the crew has no independent and clear confirmation of where they are. They fly blind, relying on the FMS
IO540,
Please do not try to drag professional pilots down to your own level.
Instruemnt rated pilots have been flying for far longer than GPS or even FMS has been available.
To say that someone who does not have a GPS will not know exactly where they are all of the time shows a total lack of understanding with regard to simple basic radio navigation.
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To rely on a unmonitored, unapproved navigation aid which the manufacturer and the authorities restricts to VFR flight only to monitor another aid which while being approved is also unmonitored is no better than relying solely on the unmonitored one (either one) in the first place because when they tell you different info.......which do you use?
Every approach aid has a height crosscheck at some point. There is no such thing as an approach without one.
Regards,
DFC