Ron Natalie writes:

CHORTLE. Have you any experience with a real INS. A real INS can't
find squat without being told where it is starting from. This has
to be boostrapped from other navigational devices. It's long term
stability isn't any better than a compass. It needs additional
input.

Not to find true north. It can find true north all on its own.

Your GPS and INS are useless without a chart or their internal
electronic equivelent.

I have a GPS with no chart and it's extremely useful.

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