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by juiceandjuice 5361 days ago
This is the Foucalt method.

We just measured the distance with a microscope, a 4 meter setup with a mirror to double the angle. It took about 2 hours and the only electronics were the rotating mirror. Our error was within 1%.

You can do the same thing with a 1000RPM mirror and about 50 feet with a caliper and get with 3% I suppose, as long as you are lined up good with the rotating mirror.