Our varios and GPSs tell us, amongst other things, our altitude. But which altitude? For a given position, at least three different readings can be arguably "correct". When it comes to respecting airspace this uncertainty isn’t practical.
Our varios and GPSs tell us, amongst other things, our altitude. But which altitude? For a given position, at least three different readings can be arguably "correct". When it comes to respecting airspace this uncertainty isn’t practical.