TT GPS - A Square Wheel

[daveoftruro]

As I sit here in the garden outside my house, the GPS on my iPhone Map app has me placed about 5 metres from my actual location - just across the road.

TT is saying: "Can't get a GPS fix. Do you want to use last known location."

WHY?

When you have a perfectly acceptable GPS system on the iPhone, which is used by lots of proprietary apps, why have TT designed their own, and produced an inferior system?

I can accept that under some circumstances, TT GPS might produce a better fix. But when it can't produce any kind of fix, why not fall back to using the iPhone's GPS? At the very least, it would give a fix as soon as the TT app was started up.

When you redesign the wheel, you should make certain it's not square.

 

[wombat94]

I think you are misunderstanding what TomTom is doing.

The TomTom app does not have "its own" GPS. When it comes to location, no iPhone app has "its own" anything.

iOS provides location information to all apps on an iPhone - the Apps are not allowed to get location data directly from hardware - they have to get it from the OS.

When the OS provides location data, it also provides some sort of quality indicator.

As I understand it, there are (at least) 3 levels of quality that can be set for the location data that the OS passes back.

In increasing order of quality of fix they are (I believe):

1. Location based on WiFi data - visible public and private wifi hotspots can give you a reasonable fix on your location
2. Triangulation from cellular phone towers - much more accurate than 1, since cell towers are very well known and their location is very well know and they don't move.
3. a GPS fix - obviously the best option - there can be multiple levels of GPS fix accuracy based on the number of visible satellites, but any GPS triangulation is much better than either 1 or 2.

If the TomTom app says that it doesn't have a GPS fix, then the operating system of the phone doesn't have a GPS fix - the location data must be coming from one of the other options, which could be accurate (in your case you said you were within a few meters) or it might not be depending on where you are - if you are out of range of cell towers or WiFi, that location might be wildly inaccurate.

I think TomTom won't navigate unless the location data is a GPS fix - it makes sense, since you want to be sure you have a real GPS fix to use a GPS navigation app.

 

[daveoftruro]

That's interesting info, and you're right - I've just tried turning off my wifi access and sure enough, the fix on my iPhone map app deteriorates. I'm not certain how it's determining the location of the wifi hub - it's certainly not the same as the Post Code, as that's a little further up the road.

I'm pretty certain that TT uses cellphone triangulation if it can't get a GPS fix, as I (and others on this forum) have seen messages such as "Data Roaming is Turned Off" when my own 3G network is not available, but only when using TT.

However, it still begs the question as to:

1 Why TT have decided it's better to give up providing route directions, rather than making use of the best info available (wifi);
2 Why there appears to be some kind of lock-up which is only cured by doing a cold reboot of the iPhone. I have witnessed that, as have others on this forum. In my case, it was after I'd used TT for around 200 miles, including through some tricky, sunken Cornish lanes with tree cover. Then, on a motorway with a wide open sky, TT GPS simply turned off, although the map app continued to give me a good spot. It took me around an hour to find the cold reboot cure for TT.

I see from others on the forum that S/W 1.5 has been released, although it's not in my App Updates list yet. This is reported to cure the lack of live traffic info. Is it too much to hope it also cures this problem?

Many thanks for your input.

 

[runarg]

I see from others on the forum that S/W 1.5 has been released, although it's not in my App Updates list yet.

Only USA/Canada is released as V1.5 yet. All the others are still V1.41, but will soon be upgraded to V1.5

 

[mvl]

I'm not certain how it's determining the location of the wifi hub

iPhone rents a list of wifi locations from skyhook. Skyhook is a company that drives neighborhoods and logs the location of wifi routers. It looks at unique serial numbers that are always transmitted by all wifi routers.