On Wed, 03 Feb 2016 16:52:03 +0000, T i m wrote:

snip

The TomTom GPS unit(?) knows how fast it is going by triangulation and
timing of the satellite signals. Or did you add that the GPS unit
actually transmits it's speed and location up to somewhere ('TomTom
HQ') somehow? Is that what / all you have said so far or have I
missed something?

snip

I'd need it explaining further before seeing above would help. ;-)

Looks like I was close:

"TomTom GO 6100
The TomTom GO 6100 is our most advanced all-in-one GO model. Get there
faster with Lifetime TomTom Services including map updates at no extra
cost, real-time TomTom Traffic updates and speed camera alerts.
Connect your TomTom GO 6100 with MyDrive and send your destination to
your GO before you get into the car. What's more, the built-in SIM
card means you're always connected to these services, even when
driving abroad. And with no roaming charges!"

http://www.tomtom.com/en_gb/drive/ca...o-6100-europe/

So, it (well that model anyway) has a phone SIM in it and so can
upload real time data all the time (subject to range etc).

Makes sense to do it that way, as it did with speed camera points
(where you press a button on the GPS when you pass a camera and then
upload it over the net when you get home (via the dock). Enough user
inputs agreeing and they then download the info to everyone).

Cheers, T i m