Speed always returns Null

[MastaBaba]

The 'speed' property of the 'position' object always returns 'Null'. This, in the browser, on iOS and on Android.

Am I missing something obvious? Or, is there no way to obtain the device speed?

(Of course, I can calculate the speed of the device based on changing lat/lng, but that turns out to be very inaccurate, as even a device at rest sees its lat/lng continuously changed.)