Re: How do you measure SPEED on skates?

Phil Earnhardt <[EMAIL PROTECTED]> wrote in
news:[EMAIL PROTECTED]: 

> If all wheels maintained constant contact with the ground, it might be
> a reasonably accurate way to measure speed. But they're obviously not.

Good point, would work well only on downhill runs, or else would have to 
run an averaging algorithm.

> Several devices use GPS for measuring speed and distance. Timex has
> such a device; I believe that Garmin came out with a
> speed-and-distance-only device this year.

Others in this thread have pointed out the problematic performance of the 
Garmin and similar units.

> As you said in the first message of this thread, you could have a
> widget that kicked out ultrasonic pulses and measured speed/distance
> based on the doppler shift of the echoes. That has been done; someone
> made a widget around 1988 for skiers. I just saw the description in
> Outside magazine; I never saw any production units.

I seem to remember some hobbyist magazine that did the same thing with the 
sonar unit from the old Polaroid SX-70 cameras.

>... After all, the existence
> of a patent doesn't imply the existence of a market for the device.

That's why I said "LOL!!"  There's nothing there that's really new--just 
where it's applied.  Late model motor vehicles have rotation-rate sensing 
going on all over--crankshaft, brake rotors, etc... (I don't get why so 
many still have a mechanical speedo cable though...?)