On Wed, 03 Feb 2016 18:35:36 +0000, John Rumm
wrote:

On 03/02/2016 16:52, T i m wrote:
On Wed, 3 Feb 2016 16:09:00 +0000, dennis@home
wrote:

Tomtoms traffic is a two way process, the sat nav tells tomtom how fast
you are going

To clarify:

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?

All it needs to report is its location... Tomtom HQ can work out
everything else since it has a map of where every location is in
relation to every other one, and how they are connected.

Yeahbut it was 'how' it reported back I was interested in. ;-)

so if another tomtom user experiences a delay they can
inform others.

How?

For delays, simply by reporting co-ordinates not much displaced from
those of the last report.

.... over a mobile phone network data link ... ;-)

For actual map errors etc, then they have a facility for users to make
corrections.

Yes, I have done that with Garmin for our actual road (name).

They then compare multiple observations and make updates if
there is a correlated agreement.

Ok.

Perhaps with access to enough devices and time, you might be able to
game the system to prevent cars being directed down your road! ;-)

Hehe ... worth a thought (or more pertinently, massive lorries at 2am
in the rain and me going out to get them out of trouble to save them
writing off any more parked cars ...). ;-(

Cheers, T i m