I'm a bit familiar with speedometers and their accuracy when used in
commerce. When I last looked into this, a long time ago, speedometers
could be make accurate or inaccurate. And to set them to dead-on
accuracy was also fairly easy. All one had to do was to change the
speedometer gear so that it corresponded to exactly one mile with
whatever tires were on the car and so forth. As I recall, there was
really only one special speedometer shop that had a one mile track
nearby, straight, linear highway mile, that could give you exact
dead-on accuracy if requested and be tested for it. Extremely accurate.
I was surprised at the accuracy that could be achieved with just the
right speedometer gear installed.
But keep working on your notion. I see other possibilties for your idea
other than speedometers. I just wanted to post because I had actual
experience with testing old, analog speedometers and was surprised that
they could be made extremely accurate.
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