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I have also had a similar weird and worrying thing happen to me just now...
I went out to take my partner off to work on nightshift.
Unlike any other time, I never actually switched my sat-nav on at the door, but rather, some 200 yards SW from my home, at the local corner shop, where she wanted some groceries.
Now I mention this, as curiously, or just coincidentally, the error I am about to describe on my sat-nav, happened to place me around 200 yards sw from where I actually was.
So maybe just coincidence, or maybe more to it, in terms of switching it on 200 yards sw of it's normal switch on point, and last know gps location.
Anyway, I digress perhaps, the long and the short of it is that for the entire journey taking her to work, the sat-nav was well out by around 200yards, with a net result, if you picture what this would lead to, of me constantly being off road all the time, sometimes in fields, other times in totally different streets heading the wrong way as a result.
(This being in very open roads, no obstructions, and no bad weather as such tonight)
During the journey, I tried a switch off and back on, but to no avail, as well as a Wireless mobile phone/PND downlaod of the latest GPS Quickfix file, as the other thread on this mentioned that some thought this might be the issue.
Both made no difference.
So after I dropped her off, I connected up my Nokia E51 and my external BT GPS unit, to see what that said on the matter.
And it had me right where I was meant to be.
Problem is, as I drove off, and around the roundabout to come back on myself, and thus head back home, the TomTom ALSO then corrected itself.
But I would almost swear that when I checked, my Nokia maps and ext. GPS had me in the CORRECT place, while my TT had me off. So the theory of it being a satellite issue as mentioned in the other thread, would not seem to be true, if this was the case.
Unfortunately, as I say, a quick run round the roundabout, and TomTom then worked from then on too, so it's not as if I had long to check to see if they differed.
It could also have been that as soon as I reached my 'previous position' after doubling back on myself, TomTom was able to compensate for the errors.
But whatever the case, after the previous thread about this, and now it happening to me, I am GENUINELY worried about the otherwise previous good reliability of my device.
This does not bode well, methinks, no matter what the reason.[/b]
Joined: Jan 14, 2005 Posts: 19638 Location: Blackpool , Lancs
Posted: Fri Feb 22, 2008 12:01 am Post subject:
Have you recently updated the device with new Quick GPS fix data via Home? - this is an automatic process , if it downloads messed up data I would expect the nav unit to take longer to acquire a position fix, but some people on other web sites seem to be claiming the offset is due to this bad aGPS download - I never use it (as it offers no benefit IMHO) so I cannot comment other than on what I have read elsewhere) - Mike
Have you recently updated the device with new Quick GPS fix data via Home? - this is an automatic process , if it downloads messed up data I would expect the nav unit to take longer to acquire a position fix, but some people on other web sites seem to be claiming the offset is due to this bad aGPS download - I never use it (as it offers no benefit IMHO) so I cannot comment other than on what I have read elsewhere) - Mike
That's the thing Mike,
It was working fine today, and it hasn't been docked in between, yet did this tonight.
So makes the previously mentioned QuickGPSFix possibility sound less likely.
Joined: Feb 01, 2006 Posts: 2543 Location: Rainham, Kent. England.
Posted: Fri Feb 22, 2008 2:18 am Post subject:
Are you making sure you are getting a good lock on 5 or 6 sats before moving off? I say this because you'd get similar results to what's happening if you have a lock on say 3 satellites or 4 and one goes over the horizon. All the time you are moving TT is playing catch up. Simply slowing down for a roundabout or stopping at traffic lights, or stopping to drop off or pick someone up, gives TT a chance to lock on properly and find it's position. E.G. Drivng along the Teign Valley in Devon, with a good lock on 6-7-8 sats, there are several places where suddenly all but two or three sats are lost, as a result TT shows the position as driving along the river. The first couple of times this happened I kept driving and my position was all over the place. I found my stopping for a minute or two and everything went back to normal.
Alas, signal strength was perfect - I was just 'perfectly off' by 200 yards **
I even tried "Doing a GPS Configure" just in case, as other posts suggested this. Again, the signal lock was solid.
In terms of my windscreen, no it's standard.
And as a footnote, in TWO YEARS of running CoPilot 6 previously on my pocket PC, I never ever once had anything like this happen. Either I had a fix, or I didn't (which given where I live, no tall buildings or covered in streets etc, was rare anyway).
And CoPilot used afar inferior chipset in it's external GPS.
I did notice that at around the time this happened however, my TomTom Traffic Plus service showed me as having High Wind symbols right across my ENTIRE screen at equally spaced distances - I assume a way of saying, it's very windy in general tonight.
So, who knows - just very strange.
Especially as Nokia Maps located fine using the same inferior CoPilot chipset GPS.
Joined: 11/07/2002 14:36:40 Posts: 23848 Location: Hampshire, UK
Posted: Fri Feb 22, 2008 1:42 pm Post subject:
It could still have been QuickGPS to blame. All QuickGPS does is speed up the process of acquiring almanac and ephemeris data tables.
If the data was corrupt then the issue you describe could occur and it is likely that a download direct from the satellites by your unit has resolved the issue.
I have had similar symptoms on various devices on rare occasions over the years (long before QuickGPS existed) and a reset resolved it as it forces new data to be downloaded.
QuickGPS can make matters worse as if one table is corrupt, everyone who uses QuickGPS might get the same erroneous data. This is much less likely when obtaining data in the normal manner from the satellite network directly. _________________ Darren Griffin
It could still have been QuickGPS to blame. All QuickGPS does is speed up the process of acquiring almanac and ephemeris data tables.
If the data was corrupt then the issue you describe could occur and it is likely that a download direct from the satellites by your unit has resolved the issue.
I have had similar symptoms on various devices on rare occasions over the years (long before QuickGPS existed) and a reset resolved it as it forces new data to be downloaded.
QuickGPS can make matters worse as if one table is corrupt, everyone who uses QuickGPS might get the same erroneous data. This is much less likely when obtaining data in the normal manner from the satellite network directly.
I don't understand how it all works enough to disagree with that view **
In fact, it is probably fairly sound, given that one thing my OTHER Navigation devices DO NOT have, is a QuickFix data in this manner.
So the one single uncommon variable to TT, is that it is the only one that uses this option.
So maybe you are right Darren.
I just don't understand how it was working ok in the afternoon, but NOT in the evening, without any download in between - unless the way it works is to do with times etc - that might explain it.
For TT to do this TWICE in two days to people is alarming though if so - there should also be some way of then allowing us to tell it NOT to use the QuickGPS data? I mean other than a reset which would lose all my data and POI's etc I assume?
Joined: 11/07/2002 14:36:40 Posts: 23848 Location: Hampshire, UK
Posted: Fri Feb 22, 2008 2:49 pm Post subject:
shadamehr wrote:
I just don't understand how it was working ok in the afternoon, but NOT in the evening, without any download in between - unless the way it works is to do with times etc - that might explain it.
That is exactly what the tables do, they tell the device what SV's (Satellite Vehicles) it can expect to see in view at a particular time. Without this data it has to download the table which takes a minute or two before it knows which SV's to search for. So the corruption may have been for a later part of the day or a particular SV which it 'expected' to see at that time but couldn't.
An article I wrote some years back explaining the process may help explain what Alamanac and Ephmemeris data is, see here/ _________________ Darren Griffin
Grumpy head on.... couldn't this have been added onto the end of the existing topic shadamehr?
The very first thing I did was consider whether to add to existing, or create anew - hence my link to the other thread to demonstrate I was already aware there was another thread similar.
And my considered opinion was that as it was a new day, and a new case, a new thread might be better, rather than hijacking someone's else's thread.
In hindsight, it is still a matter of opinion as to which route was the best way to go, so you might be right.
Especially if this issue is going to persist for users.
Joined: Oct 08, 2007 Posts: 2544 Location: Toronto CANADA
Posted: Sat Feb 23, 2008 7:24 pm Post subject:
Andy_P2002 wrote:
dhn wrote:
Actually, the new TTHome version .2283 DOES show the correct map version and build number. Does for me, anyway.
Map maybe, but not much else! For me:
Home says:
App 7.221 (8572/040301), OS:1000, GPS v1.21, Boot 1.0012, Map v715.1710
Device says:
App 7.221 (8572/071121), OS:2318, GPS v1.21, Boot 5.4106, Map v715.1710
No argument, Andy......
But, it seems to me the most common question people wonder about is what map and build number is installed. So, I guess showing accurate values for that is a small step. I'm not even sure I remember anybody having issues with disparate boot values, etc.
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