"David W" wrote:

Hello to all,

Do most modern aircraft rely on the GPS for navigation, and to what
extent do they rely on it?

What kind of modern aircraft are you talking
about--bizjets...airliners...military?

And is it true that such aircraft's navigation systems use maps
'optimised' for GPS?

What does 'optimised' for GPS mean?

And finally, if I may, what level of positional accuracy must aircraft
relying on GPS for navigation work with at typical altitudes
(presumably 20,000 to 40,000 ft)? Are we talking tens of metres, or
over a hundred metres?

Tens of meters or less.

What's behind your questions; what are you trying to get at? If you posted
that, you might get more suitable answers.

--
Dan
C172RG at BFM