How do jogging watches measure distance travelled?

Factual Questions
1

I know how they can measure pulse rates, that is more obvious.

But I’ve never understood how the distance jogged thing works. Do you have to enter in your stride length and it measures the jiggling as one step taken? Or is it a general ‘most people run at this speed, average it out over time’ thing?

Do tell.

2

Most of them Used to work on the stride length/ joggle every step thing. I don’t know if there have been any recent advances in jogger watch technology, though.

3

I have a “years old” gadget that looks like a one-hand pocket watch called a “Pedometer”. It hangs from the belt and has an internal, lightly-sprung pivoted weight which swings through its excursion range each time a step is taken. An adjustment wheel allows you to set your stride length and the outer dial is calibrated in miles. (Exactly how many I forget right now and the device is well-hidden at the moment.) Obviously, it’s accuracy is highly dependent on how consistently you maintain your stride. I would imagine modern counterparts have something similar, but perhaps replacing the relatively large weight with a compact strain gauge.

4

Couldn’t you just but a simple accelerometer in there and just use dead reckoning? Or would that be too expensive for any useful amount of accuracy?

5

There are now watches that have a GPS system-quite pricey(for me,anyway)

6

I was just looking into this recently. The normal pedometer ones just use stride length, and suck accuracywise for runners. Okay for walkers who use a steady pace though. But they only cost $10 or so.

Nike makes one based on Shalmanese’s idea, with an accelerometer. It uses a 2 oz measurement pod on the shoe and an optional radio watch display. $125 for the pod (Nike SDM Tailwind) and $235 for the watch version (Nike Triax 100).

Timex makes ones that use GPS, as runner pat said. The Timex Speed & Distance system uses a pod that straps to your upper arm and a radio watch. $225 for this one.

7

I wondered about GPS, but I thought the accuracy of that was down to within 50m square or something. I guess it’s improved.

Well, that certainly answers my question! Thanks, guys.