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TomTom OneXL problem
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nicky1
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Joined: Aug 26, 2008
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PostPosted: Mon May 11, 2009 8:31 pm    Post subject: TomTom OneXL problem Reply with quote

Is anyone having problems with this satnav? We use ours fairly infrequently but when it is used it can sometimes lose all the satellites and then refuse to lock on to any. Getting it to work again can be a bit hit and miss; sometimes switching off and then back on some ten minutes later or other times is needs a hard reset.

When the signals are lost the strength just prior to the failure is a full five bars.

We also have a built-in satnav (and use both!); the other one never loses the signal except in a tunnel so I'm confident it's not a simple problem of not being able to see satellites.

Once failed, when looking at the status screen the satellites are either grey bars or simply not there at all; they can temporarily go blue to indicate the satnav has locked on then they go grey again.

This unit is just less than twelve months old. Perhaps it requires a firmware update or replacement? Otherwise this is a superb unit and I love driving with it.
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mikealder
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PostPosted: Mon May 11, 2009 8:40 pm    Post subject: Reply with quote

It shouldn't drop the signal in this way unless you are driving in tunnels or between tall buildings that are close together (urban canyon) When it does drop the signal if you are moving try stopping when possible as the device will struggle to locate the signal in a moving vehicle, stationary it stands a much better chance of acquiring the signal in a shorter time period.

What car are you using the device in as it could be down to the windscreen that is causing this - some use a coating of Titanium and are known as Athermic or Heat reflective screens, these seriously mess up GPS reception, the built in unit probably has an external aerial and thus works better if this is the case - Mike
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nicky1
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PostPosted: Mon May 11, 2009 9:56 pm    Post subject: Reply with quote

This is mostly when buildings are nowhere near; it's happened in the countryside in Scotland and in the Lake District. Stopping doesn't have much of an affect to regain the signal, even if the unit is held out through the sunroof.

This is in a Honda CR-V (the version before the current one) and I'm not aware the windscreen is anything out of the oridinary, it isn't heated.

The signal strength is nearly always five bars, and the moment just before it locks up the strength is still five and hasn't fallen as I would expect it to have if it is signal problems. We purchased this from Amazon around eleven months ago so if it's dodgy then I guess I need to report it before the year's warranty runs out!
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george57l
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PostPosted: Tue Jun 23, 2009 10:33 pm    Post subject: Reply with quote

Hi - did this get resolved (naturally or otherwise)? I have a TT One with similar issues now.
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mikealder
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PostPosted: Tue Jun 23, 2009 10:56 pm    Post subject: Reply with quote

One other thought is duff qGPS data supplied via the TomTom Home software, have you had the device updated recently as there have been a few problems with qGPS reported in the USA, but this also means it could be affecting European usage from time to time - Mike
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george57l
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PostPosted: Tue Jun 23, 2009 11:17 pm    Post subject: Reply with quote

The TT One in question has never been connected to TT Home, or had its software or files changed at all since taken out of the box. Makes me think "hardware failure" more than anything... but I'm hopeful of some other explanation.
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Snudge
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Joined: Aug 22, 2007
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PostPosted: Wed Jun 24, 2009 10:47 am    Post subject: Reply with quote

I had a similar problem yesterday Ė One XL mounted on bike powered from bike battery going from Peterborough to Hunstanton. Started off ok about 10am and quickly got gps signal but after about 7 miles I notice position had drifted and signal strength meter had dropped to 2 bars and then none. I was on open road with no tunnels, trees or tall buildings. It didnít get signal back so I stopped for about 10 minutes but no signal. I didnít have a paper clip to reset device so left it on but it never worked for remainder of journey. When ready to return home about 3.30pm I mounted sat-nav on bike and it got a signal very quickly with full 5 bars showing and it was ok all the way home Ė about 80 miles. I still havenít done a reset but this morning it quickly got a signal inside house, not near a window either, but showing 7 satellites.
Iíve owned the XL for nearly 2 years and itís always worked perfectly Ė I havenít connected to Ďhomeí for over a year so itís not a bad quickfix. I logged onto this site expecting to read that there had been a problem with the satellites (is that even possible?) so was my problem connected to those of nicky1 or george571?
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george57l
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PostPosted: Wed Jun 24, 2009 12:32 pm    Post subject: Reply with quote

Update:
Despite huge misgivings (been there before and never going there again - but it's her TT and PC, not mine) other half installed TT Home, updated quickgpsfix thingy and this morning it is working fine again. Fingers crossed.

But can anyone explain what sounds like black magic - how can the TT unit "know" where to look for sats and how can it "lose" them? I've read stories of 'not switched on for weeks' and 'took it abroad' where this is alleged - the implication being that there is something somehow 'directional' inside the TT unit that needs to be looking in the right direction or it can lose satellites - and it loses knowledge of the 'right' direction too look in if it is not shown a satellite often enough or is transported miles from where it last saw one. The qquickgpsfix thing with 7 days data re sat positions clearly implies the same sort of voodoo.

Really? How?
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george57l
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PostPosted: Wed Jun 24, 2009 12:33 pm    Post subject: Reply with quote

PS - and like Snudge - why would it happen mid-journey? (!!!!!)
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Darren
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PostPosted: Wed Jun 24, 2009 12:38 pm    Post subject: Reply with quote

george57l wrote:
But can anyone explain what sounds like black magic - how can the TT unit "know" where to look for sats and how can it "lose" them?

Have a read of this article.
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george57l
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PostPosted: Wed Jun 24, 2009 12:56 pm    Post subject: Reply with quote

Darren - thanks. I recall reading that article a long time ago - forgot it was there. I think the issue I have is that in other forums/posts/descriptions I have seen the word "look" used many times. The GPS unit does not "look" any more than my TV or radio does, surely? It is just as passive. It may have to receive and track a signal for a period (satellite saying "I'm here", "I'm here, now", "I'm here now", etc) and it may have to do it for multiple satellites, before it can tell where it is on the sphere, but "looking" is one thing it is definitely not doing.

Maybe I'm being pedantic and splitting hairs but the impression given elsewhere, that if you tell the GPS unit where the satellites are it will "look" for them, is misleading. If you tell the GPS unit WHERE THE SATELLITES WILL TELL IT THEY ARE, then it will improve the process (and speed) of locating itself, is perhaps more accurate. Or am I holding the wrong end of a long thin wooden thing?

Anyway at least I think I get it now. ;-)

What still bugs is that having lost signals mid journey (halfway across Kingston Bridge FFS!) it seemed to be a permanent loss until a day later quickgpsfix was installed. I call it a 'hissy fit'.

Thanks again,
George
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Andy_P
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PostPosted: Wed Jun 24, 2009 3:17 pm    Post subject: Reply with quote

You're right of course... Smile

We're all guilty of lapsing into lazy phrases like "looking for satellites" sometimes. What is really happening is the satellites TELL the sat-nav where they are.

I posted something about it a couple of weeks ago:
Quote:
There's a couple of widely-held misconceptions rearing their heads again here....

Firstly, no sat-nav can "find the satellites where it is going to initially look for them" as it only has a single not-very-directional aerial and is a passive receiver.
It actually just receives data from the various satellites saying where THEY thought they were at a particular time (the ephemeris and almanac data), and the sat-nav number-crunches that to work out it's position by a sort of triangulation (more correctly - "trilateration").

Secondly, if you powered off the sat-nav for ANY time the satellites most certainly WOULD have moved! They are not geo-stationary, they are whizzing round at about 8,300 miles an hour, making two orbits a day.

What methods like Quickfix do is allow the unit to use published ephemeris data, before it has had time to collect the real thing from the satellites.
Quote:
While the ephemeris data is transmitted every 30 seconds, the information itself may be up to two hours old. If a fast Time To First Fix (TTFF) is needed, it is possible to upload a valid ephemeris to a receiver, and in addition to setting the time, a position fix can be obtained in under ten seconds. It is feasible to put such ephemeris data on the web so it can be loaded into mobile GPS devices.


LOTS more info (more then you could ever want!) on Wikipaedia HERE
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Snudge
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Joined: Aug 22, 2007
Posts: 211
Location: Peterborough

PostPosted: Wed Jun 24, 2009 4:11 pm    Post subject: Reply with quote

Ok, I don't think my sat-nav has developed a fault and I think I may be able to explain the loss of my gps signal
Ė it could be MOD jamming trials HERE
Quote:
Jamming trials happen more than we think.

The Ministry of Defence last year carried out a series of GPS jamming trials to find out how interference could affect military personnel.

In one test it jammed GPS over a 50 square mile area of Cornwall over two days, warning emergency services and coastguards in advance.

In a statement issued at the time, it said: "Although GPS provides highly accurate information, the radio signals from the satellite are extremely weak and are susceptible to both jamming and unintentional radio interference.

if you want emails when jamming is proposed sign up HERE

Ö..unless anyone has any better ideas?

(Perhaps this isn't why george lost his signal on Kingston Bridge though.)
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george57l
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PostPosted: Wed Jun 24, 2009 4:42 pm    Post subject: Reply with quote

Thanks, Andy_P. That concludes that part of the discussion. ;-)

As for Kingston bridge -well it wasn't me it was the other half so it could have been "around" there. Lots of tall buildings and a couple of "under bridge" experiences on the roads around Kingston...

But the real mystery for me and the real bugbear is still outstanding. If GPS unit loses signal for a second or three - why does it take literally hours (and in fact only a quickgpsfix update) to get it receiving again?
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obeone
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Joined: Jun 19, 2006
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Location: Dalton-in-Furness

PostPosted: Thu Jun 25, 2009 8:24 pm    Post subject: Reply with quote

Hi, just to comment on Snudges post.
I had same problem on Wed 24 at about 11.00. Just turned off the M1 at Junction 13 (nr Bedford), there were masses of roadworks and for the next 6-8 miles TT showed me driving along in the fields next to the road.
Unit was constantly re-routing. I stopped and turned off/on but it wouldn't lock on.
In desperation tried a re-set and unit then worked perfectly!.
TT has lastest map updates/gps fixes installed.
Heh Ho!
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