GPS finds true north. And, just incidentally, you can find true north by
looking at the sky. ANS will do that, and people can do it, too.

As an expert in Location based services and GPS, let me assure you
that depending solely on GPS for any form of navigation is a fools
errand that is going to get a lot of people killed one of these
days.

The system is a rube goldberg contraption with an instant-on kill
switch. Wait until someone launches a home-made GPS guided cruise
missile into Washington DC, watch them flick the switch, and see what
happens. Just hope it doesn't happen at night, and you're not in the
air at the time.

Documenting them doesn't really eliminate them.

It does make you aware of them, which is all you need.

GPS is better, and more accurate, to name just one.

It also requires constant, very expensive maintenance, a complex
receiver in good working order, and as I mentioned, can be turned off
at the push of a button. None of these are traits you want for you
primary navigation system.

You can find true north by looking at the sky, or with GPS, or with ANS
(automated looking at the sky), or with an INS. The latter usually has to be
on the ground, although some systems support align-in-motion with a longer
setup time.

The simplest, fastest and most dependable (in VMC) way of finding true
north (or any form of navigation) is simple spatial awareness and
pilotage. A good chart, and a good eye.

You need a precise clock to do just about any navigation. The need for the
rest is debatable, depending on how resourceful you are.

Not at all... about the only modern navigation that requires a precise
clock is night over uninhabited terrain or over water.

Unless the airplane is a glider, you have power.

GPS have batteries, power isn't the issue. The problem (in my
experience) with GPS is that they're _SO_ good that people very
quickly delegate all of their navigational requirements to them,
letting their pilotage, dead reaconing, and other navigational skills
atrophy (in my humble experience at least). This is fine, until the
tremendously complex system finally fails (either intentionally or
otherwise). Either way, its not something I want to bet my life on.

One third correct: it requires power, but engines provide power. It doesn't
have to be set up against anything else to find true north. It doesn't need
to be constantly updated; the whole idea is to be fairly autonomous.

The whole idea of navigation is to know where you are in space at any
given time. Autonomy is irrelevant.