Judah writes:

You can use multiple points to determine your location with a fair amount
of precision, and you can estimate with a fair amount of accuracy your
distance from the landmarks.

Even as you are flying? There are a lot of airspaces to worry about.

Where is this?

Many places. By the time you've carefully calculated whether or not
you're in one of them, you're no longer there, but you've violated two
other airspaces. Even in small private planes, things move quickly.

How wide, exactly?

A good ten miles or so, at least, depending on many factors.

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