TomTom START 52

Charging it in the car using the TomTom charger was spectacularly fast, so much so that the charger became too hot to handle.

Thanks. My thoughts too. I stopped using that charger and bought a replacement. I think I might stop using TomTom too in the future.

There are plenty of free online and offline sat nav apps for both apple and android that are much superior to TomTom.

As far as I am concerned , it's the quality of the traffic information that matters. TomTom was - when I last used it - extremely good.

The traffic information in Google maps is derived real-time from the phones in the cars of everybody who is using Google maps. It's difficult to see how this massive crowd-sourced data solution could be improved upon. I use it all the time for traffic information, and am very impressed.

In some jurisdictions, it isnt just those using Google maps, its all mobile phones moving in cars as seen from the mobile phone bases.

By using all mobile phones obviously moving in cars.

That's the one that TomTom uses, too. My Mazda uses another source of data which is useless.

Presumably only those phones which have GPS turned on so the phone can report its position and (more importantly for congestion reporting) its speed. Knowing which phone base a phone is connected to will only give a fairly crude report of where a phone is (maybe only "somewhere within the reception area for this mast", maybe some crude triangulation from time delays of packets to neighbouring masts will allow a little more precision) and will not give speed.

Unless mobile phone info is more elaborate that I thought.

I'm often bewildered by how *inaccurate* the reported position of a phone is, using the Location Sharing feature of Android phones. Firstly it sometimes lags by many minutes or even hours, and secondly it sometimes positions the phone a long way from the correct position. When I am "following" my wife coming home (we use location sharing so if she phones with traffic problems on her way home from work, I can see where she is to suggest an alternative route) I can see her at various places on the route, and then suddenly the next reported position will be several miles off the road, sometimes many miles further back. Either her phone's GPS is not working (and in other situations it works perfectly) or else the phone fails to report its position for many minutes or it uses some technology other than GPS to decide where the phone is.

Sometimes killing and restarting the Location Sharing app (a link to Google Maps with the phone's position marked on it) will result in an updated position when it has been stuck in one place for half an hour or more.

Does anyone who for certain what technology Location Sharing uses to determine position and how often it should update the reported position - assuming a mobile data connection, of course.

I/we have used

Google use a combination of GPS, wi-fi (they keep a log of wi-fi SSIDs and their locations) and mast position to work out your location.

From your description I would guess that whatever app you use does not rely on GPS but probably on the masts' location, which is very inaccurate. Alternatively the app that you use may be rubbish...

But how that changes over time does.

Yes, that has nothing to do with what the mobile bases can see of the traffic with phones it can see.

This app

shows a map with the locations as reported by GPS, by a WLAN lookup, and something or other ("passive", "network", and "gps").

I've had large errors (~1 km) when the phone picks up a single WLAN signal, and the algorithm places the phone at the WLAN location. How the phone can pick up a signal that far away and still have poor WLAN reception from a source two doors away -- I have no idea, some freak of propagation I guess. A GPS fix leads to a divergence of the GPS location and the network location.

The app also shows the mobile cells and their signal strengths.

Thomas Prufer

A thought. Beacon frames - that announce SSID - may not need huge bandwidth or strong signals.

All it ned to get across is a MAC address to uniquely ID the wifi ..

A GPS fix leads to a

So do phones keep track of WiFi router MAC addresses and their corresponding locations, and feed them to a central database that is then used as a low-tech way of determining where a given phone is? No wonder the location that is reported is vague or wrong, if the phone's not using a proper GPS fix.

The bigger problem I have with Google Location Sharing is the infrequency of updates, irrespective of whether the reported location is correct. Very often I find that the location freezes for several hours, and it's inconceivable that the phone has not been able to determine its location and/or report it by mobile internet some time during that period. I can't work out whether it's a problem with the reporting phone or with the phone that is displaying the other one's location on a map.

Another thought here. Are you saying that such a charger could effectively have destroyed the battery on day 1 and the fundamental problem was the charger rather than the battery?

Not the phone, Google...

I seem to recall that they were forced to stop the practice once it was made public though.

Google need to acquire that list of MAC addresses / SSIDs and the corresponding GPS locations in the first place so they can give an estimate of a phone's location from the wifi networks that it can see. I had originally thought that such a list was generated by "crowdsourcing" - using reports from people's phones which have both wifi and GPS turned on and so can send MAC and GPS. But the article says the scan is done by the Google Streetview cars as they are taking photos of each street, so once every few years.

There are bound to be errors in such a list if the owner of a router moves house and so the MAC address is now associated with a new location and not with the old location. I wonder if that is why my wife's location on her way home sometimes jumps backwards or to a completely unrelated place during her journey.

I presume the reason Google use this is because it allows people to turn off GPS (prolonging battery life) and just leave wifi turned on - but at the risk of getting incorrect locations. And I presume that in the event of a GPS fix and a wifi MAC address fix, it always uses GPS in preference because the wifi MAC location could be wrong if someone has moved house.

I remember when I first got a smartphone with GPS, I found that map fixes were totally wrong, placing me somewhere in the Mediterranean. Rebooting to force the GPS receiver to reacquire the satellite almanac didn't help. What did help was turning off the use of wifi networks as an aid to location.