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It's a fundamental principle thing, that has some knock-on practical effects. Navigation is fundamentally getting from point A to point B. To do that, you steer

It's a fundamental principle thing, that has some knock-on practical effects. Navigation is fundamentally getting from point A to point B. To do that, you steer a course between the two. Do you want to describe the angle of that course in reference to (a) A fixed line that never moves, such that the angle ('bearing') of that course is always the same (b) A line that moves around, seemingly randomly, particularly if you are near one of the poles of our planet Obviously from first principles, you'd pick the first. Due to historical navigation technology it was more convenient to use the second though. We had an instrument (magnetic compass) that would directly give us reference for (b), and so we described everything in those terms, and maintained tables of offsets so that we could calculate (a). Using (b) - magnetic North - causes some problems and because very few aircraft, and no commercial ones, rely on magnetic bearings as a primary source of navigation those problems are not worth it. One of the problems comes when you start labelling things that are fixed relative to (a), because they're attached to the ground but you label them using (b). After a few years the labelling is wrong and they need relabelling. This requires everything from pointing of radio beacons to repainting runways. It's all needed for effectively historical reasons. There are two Norths: The one that points in a constant direction on the Earth's surface. Getting from point A to point B on the Earth is fundamentally what navigation is and so having a fixed reference for that is good (modulo continental drift). The direction that a magnetic compass points. This is at an arbitrary and changing offset to any direction on the Earth's surface. Why

flavius29663 5y ago
Now I get it, using the magnetic north is akin to the daylight saving time kerfuffle, on steroids - you basically have to account for variations even during the same flight if you fly near the poles.
- Grustaf 5y ago
  The magnetic north is even affected by local phenomena, at least when you're on the ground, so it's worse than that.
ryandrake 5y ago
> (a) A fixed line that never moves, such that the angle ('bearing') of that course is always the same Just to nit-pick your otherwise great comment: This may be true for short, general aviation navigation, but long haul airliners typically navigate via great circle routes, which do change true course throughout the route.
- rkangel 5y ago
  Yes, there's lots of reasons why you don't fly in a straight line from airfield A to airfield B. Whether that's a great circle or just a multi segment line to avoid an airspace restriction I suppose what I was really talking about was "your bearing at any given moment on your course".
Grustaf 5y ago
I'm aware of all this, it's the same in sailing and it's a mess. But since aircraft are already set up to use magnetic north, and are basically flying computers, it shouldn't matter what crazy navigation scheme they are using. But a sibling comment already pointed out, what you also mention, that it also affects physical markings etc, and that makes much more sense.

flavius29663 5y ago

Now I get it, using the magnetic north is akin to the daylight saving time kerfuffle, on steroids - you basically have to account for variations even during the same flight if you fly near the poles.

Grustaf 5y ago
The magnetic north is even affected by local phenomena, at least when you're on the ground, so it's worse than that.

ryandrake 5y ago

> (a) A fixed line that never moves, such that the angle ('bearing') of that course is always the same Just to nit-pick your otherwise great comment: This may be true for short, general aviation navigation, but long haul airliners typically navigate via great circle routes, which do change true course throughout the route.

rkangel 5y ago
Yes, there's lots of reasons why you don't fly in a straight line from airfield A to airfield B. Whether that's a great circle or just a multi segment line to avoid an airspace restriction I suppose what I was really talking about was "your bearing at any given moment on your course".

Grustaf 5y ago

I'm aware of all this, it's the same in sailing and it's a mess. But since aircraft are already set up to use magnetic north, and are basically flying computers, it shouldn't matter what crazy navigation scheme they are using. But a sibling comment already pointed out, what you also mention, that it also affects physical markings etc, and that makes much more sense.