Originally Posted by
Ninthace
In the days of Flight Systems training at Cosford, we taught the basic theory of inertial navigation. All examples involved ac flying E or N or even NE. Any other direction involved negative numbers which the would-be techies, being products of the then educational system, had trouble coping with.
Slightly OT, but related - I'm reminded that for many years one of the first of the enthusiast ADS-B receivers (RadarBox) suffered from a 5 million square mile equatorial "black hole", whereby it was incapable of decoding coordinates between 2°S and 2°N, so if you wanted to use your shiny new box to track aircraft in Singapore, Nairobi, etc you were in for a nasty surprise.