The TomTom BT GPS Receiver you're using has the SiRF III chipset which is very good and can even track reflected (weak) signals from the satellites using it's 20 channels. It can usually get a lock in seconds. That it didn't must have meant very poor line of site to the satellites etc. Or something else was up with TomTom Mobile which has not got the best reputation for reliability - I have it.
The TomTom software running on the mobile cannot assume anything about position. Lost signal means just that. And in fact the GPS chipset is doing it's own thing and communicating over bluetooth to your mobile running TomTom - and this case saying no valid GPS signal. If the GPS receiver battery was flat how long should TomTom software guess?
The original TomTom standalone unit (expensive at the time) had a gyroscope to help it when it lost satellite signal. And a proper car inbuilt GPS unit has both gyroscopes, links to the car speed sensor and reverse gear sensor - so when they lose GPS signal the unit knows your road speed and direction and can still update the map position. One reason a dedicated car GPS unit still a lot more expensive than a PND one.
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Wow - I learnt more about Sat Nav in that one post than I ever knew boefore. SWMBO says "gwych".
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So Pugugly you remember I am Welsh. Thank you. Or I should say "diolch yn fawr".
The best place to find out more about sat nav on PDA/Phone/PND is pocketgps.co.uk. A site I'd recommend for satnav like I'd recommend this for car stuff. Or I'll try my best here. Especially TomTom 5 mobile issues on a Nokia N70.
But I am a computer type person so I like tech stuff.
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well the tomtom5 running on my IPAQ knows what speed I enter the hatfield tunnel, assumes the same speed throught the tunnel plotting the position (tho greyed out) and picks up 5 seconds at the other end.,
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TourVanMan TM < Ex RF >
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SWMBO's Tom Tom tracks through tunnels quite happily (TT7)
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Depends on how long in the tunnel, type of GPS receiver to quickly re-establish signal, and also what the surrounding area is when you get out.
All latest GPS receivers from TomTom (including Bluetooth GPS Units, TomTom One, One v2, 5x0, 7x0, 9x0 and Rider) use SiRF III chipset and so do many others. There is even a Fujitsu chipset that tracks even more channel than SiRF III - I think 32. (Plug for Fujitsu who I work for)*
OP didn't say what GPS device they have. Mine is a Navman Bluetooth from a few years back and works. But lots of people (maybe not OP) have gotten hold of TT Mobile (hacked) and then use any old cheap bluetooth receiver and then complain when they have problems.
But for example on a Nokia N70 running TT Mobile 5, there is a bluetooth issue which on earlier Nokia firmware could crash the phone even. Using latest firmware helps a lot and I've found when I went to v3.x.??? it was better then using Nokia's self updater I took it to v5.0609.2.0.1 and it's even better. I think if I had a SiRF III based GPS unit it would not have any problems. But used my PDA and TomTom the other week and realise the small phone screen is way to small.
But I do like the new small TomTom One v2. Neat. But the 510, 710 and 910 accept the new TMC adapter for free traffic info... hmm. Unless you're in Glasgow of course.
* Before someone says there are never more than 12 GPS satellites in view at one time, them being in geo synchronous orbit, I know. But the newer ones with 20+ channels track and process reflected signals so use the extra channels even if many fewer satellites in view. Hence better in urban canyon situations. And speeds up cold start up times.
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SWMBO's Tom Tom tracks through tunnels quite happily (TT7)
My iPAQ 2210 / TT5 combo does too, even to the extent in Munich of predicting when to tell me to turn right, correctly, in a tunnel near the Olympic stadium!
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"And a proper car inbuilt GPS unit has both gyroscopes, links to the car speed sensor and reverse gear sensor - so when they lose GPS signal the unit knows your road speed and direction and can still update the map position. One reason a dedicated car GPS unit still a lot more expensive than a PND one."
Blimey! So that's why mine still works going under the Dartford Crossing - I'd been wondering about that for years. Thank you RTJ ;-)
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Funny you should mention Dartford. The end of last year went to one of our company locations in that vicinity. Every time I drove through some of the tunnels on the M25 before the crossing... TomTom on my PDA would lose satellite and NEVER pick it up again. Turn off/on GPS and back to normal. It was as if the GPS receiver got confused. Happened every time I went there including this year. About 3 times and always at that point.
Phoned a colleague when stuck in the Dartford Crossing once when heading from the Hilton to other side of river - slow traffic. He would not believe me you get a Vodafone signal for most of the journey into the north tunnel until I proved it. He thought I was at the hotel having a lie in or something :-) GPS signals would not get that far because so weak and the satellites are 12,600 miles away!
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You should have signal all the way through, its got a cell repeater via leaky feeder throught it now I understand.
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TourVanMan TM < Ex RF >
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Never lost a signal ever with my nav system. had an odd crumpled page to contend with but thats it!
Imo they could be useful for delivery drivers working in an unknown area (i know several lorry drivers who will not use them because of the roads it tries to take them on etc). But have yet to understand the need for them.
I do travel a bit too btw, including europe.
Enlighten me?
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I've not used the Road Angel in conjunction with the in-car SatNav through there. I'd be interested to see how the RA got on.
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I have a theory that when TomTom has no signal for a lengthy period of time it issues a 'cold restart' signal to the GPS receiver. Receiver then takes a long time to re-acquire.
I believe on my TomTom (v5.21) it assumes last GPS speed when it loses a signal and greys-out the route (as someone mentioned above)
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That's an interesting theory... SiRF III chipset cold start a lot quicker than my old Navman unit so you could be right here. And because SirF III fast does not care.
I like TT3 when you could get a quicker fix by selecting where you are on the map and then telling the GPS this info. On cold restart of my "old" GPS receiver it went from minutes to seconds. All down to Almanac data etc. I guess.
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I am with whoever said about maps earlier...... enlighten me as well?
The only benefit I can see is being warned about roadworks or other delays, but it seems to me that one is too reliant on a dodgy satellite. I'll stick to my Traffic Report Monitor on the radio! Seems to work just as well.
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Splendid advice from my driving instructor back in the mid '70s,
"Never leave on a journey without knowing your route in advance, more accidents are caused by people dithering at junctions than you think."
I always have a short list of my route on the dash - just a list of road nos or major towns - works fine for me and with road atlas at £2.99 in my local supermarket I reckon I have a century or so to go before they have cost as much as the cheapest satnav unit.
Cheap satnav is just that - cheap - as many of the features as possible are stripped out in the interest of hitting the target price and the most obvious "rarely used" feature is route persistence through tunnels so thats why it is not implemented except on high end systems.
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It's still cheaper (and easier IMO) to buy an A to Z for built-up areas, and write down your route in full. The worst that can happen is that you might have to pull over for 30 seconds to check where you're going. I've done a lot of long-distance driving, and never needed satnav. Even driving through towns/cities that I'm not familiar with, I get a vague idea from a map before I drive. Easiest way to save a few hundred quid IMO.
As for "high-rise construction" around the tyne tunnel, there isn't anything in my memory that counts as that. But I suppose when you're paying more attention to your satnav than your road/surroundings, you wouldn't notice! ;-)
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