Are sectional paths correct across "long" distances?

vincent p. norris writes:

I can't see the red GC line very well except against the dark brown of
the higher elevations; but it seems as if the two lines are only about
a line-width apart. I wouldn't consider that "significant," but of
course that's a personal judgment.

It's personal until you cut across restricted airspace by that much.
Then it gets *really* personal.

My reaction is the opposite of yours: I'm impressed by how well the
straight line follows a Great Circle.

I'm pursuing perfect solutions. As usual, the more I get to know
something, the more I realize how little I knew about it, but I know
how to handle this now.

Can you tell me how many nautical miles separate the two lines, at the
point of widest divergence?

-102.934677557 40.1266731277 5.99724483075
6nm

I don't fly that path non-stop though. With a landing at Centennial,
the max. error is under 2nm on the leg from Indiana, and under 1nm on
the next leg to California.

I have discarded routes because the straight paths clipped some
restricted airspace by only a mile or two. I expect any tool that I
use to be accurate enough to tell me whether or not that's going to
happen.

--kyler