Speedometer Accuracy to 1/2% Accuracy - Here's How

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.