Carminat location is 122 miles from reality

[BigVan]

Hello,
I am new to this, or any actually, forum. So excuse me if I get the protocol wrong, I mean no offense. I have joined this group as this seems to be where the knowledge resides, having tried everything else.
My problem is this: I had a Poptop roof fitted to my 2011 Renault trafic van. The fitter decided to disconnect the aerial as he felt it was in the way. I drove home and noticed the satnav being strange but when I got home I plugged the aerial back in and the screen now shows my present location as being in Newbury, 122 miles away. I have tried all the uploads, updates and exhausted the very helpful chap at TomTom but nothing can persuade the satnav to show it's true position. I have fitted a new aerial, plugged it into the back of the unit. The unit says it has located 7 - 8 satellites but still insists that it is 122 miles away. Another thing, if I try the soft factory reset in the menu it does nothing and just goes back to the map screen. HELP!

 

[Willy875]

Hi

Is the icon indicating your location greyed out?

Have you tried leaving your GPS on for at least 30 minutes in an open area with a clear view of the sky—away from trees and buildings?

 

[BigVan]

Hello Willy, thanks for replying.
The map actually shows a place outside Newbury and if I set a course for where I am it says 122 miles etc. Every journey I input starts from Newbury. I have tried leaving it on until it eventually switches itself off. I have the latest updates and even bought the latest maps. By the way, the boffins at TomTom have sorted the time problem and it now displays the correct time. Whether it is set to the correct date I don't know.

 

[Willy875]

You have removed the antenna, so the problem must come from it; the GPS antenna may be oxidized or not making good contact with it.

 

[BigVan]

I bought a new GPS aerial and plugged it in the back. The unit finds 7 or 8 satellites.
It's maybe a bit like the date rollover problem from a few years ago but something must have been triggered by the disconnection of the original aerial. I have tried several times to do a factory reset from the menu but it refuses to reset.
If I go "Menu - help- where a I?" it says I am just outside Newbury, 122 miles away.

 

[canderson]

Hello Willy, thanks for replying.

One of Willy's unanswered questions is quite important:

"Is the icon indicating your location greyed out?" That would indicate that in spite of seeing some satellites, the device is still not convinced is had adequate data for a good location fix.

I'm guessing that you had the pop-top installed in Newbury?

 

[BigVan]

There isn't a greyed out icon, just a map of somewhere in Newbury and a little blue arrow representing my van.
I've never actually been to Newbury although I'm sure it's very nice.
My theory is that somehow the unit has lost track of date or time and so the calculations as to where the satellites should be have all gone pear shaped. How that happens if that is the case, and how to put it right, is a great mystery to me.

 

[JuergenAMS]

You probably need to enforce a download of QuickGPSfix data. First factory reset the device, then soft reset it. Steps are published here: https://help.tomtom.com/hc/articles/35672275934354

 

[BigVan]

Thank you for your suggestion.
Believe me, I have tried all that. I have had a very helpful TomTom operative helping me for ten days and all that was suggested and tried until he finally said to take it to a dealer. A Renault dealer? It's 15 years old!
I have pulled fuses and waited to force a reset, ignition on, ignition off, open doors, wait, download, upload, update complete maps, update quickGPSfix several times, format card, re-install software..... nothing. I even tried Google's A.I.
The reset function in the menu does not do anything, does not do a reset, just goes back instantly to the map of a street in Newbury. Trying a hard reset by pulling the fuse and waiting does not do anything.
Thank you though. It's an intriguing problem and a very annoying one but I'm confident we'll find the answer.

 

[Willy875]

Did everything work correctly before the pop-up roof was installed and the antenna was disconnected?

If nothing works now, don't you think the antenna might be the problem?

You mentioned buying a new antenna; why not put the old one back on?

As for the date and time, they will update automatically via satellite.

 

[BigVan]

OK, all is well and peace is restored once again, if not worldwide then at least in the dash of my van.

The van was parked up all week with a clear view of the sky and I could see the TomTom was capturing satellites but it was not updating my position. Well, I took the van out for a drive today and within a short distance it figured out where we were and went back to normal.

Thanks to everyone for your suggestions. As is often the case the solution was under my nose all the time.

So, lesson learned.

The new GPS aerial is a thing I got from Amazon for under £10, a small black square with a 3 metre cable that plugs into the back of the satnav, and it is amazing. You can find a home for it in the roof lining or even apparently stuff it into the dash out of sight and it still works.

The soft reset still doesn’t reset but hopefully I won’t need it to.

Apologies to the good people of Newbury. I didn’t mean what I said.

In desperation I almost went for an all singing all dancing unit from Amazon to replace the TT but I’m glad I didn’t. The tech from TomTom was so helpful and patient, imagine trying to get any help from someone over in China!

Also, I like the built-in TomTom, it works without being linked to a smartphone and on the whole is very good.
Someone on here said to hold down a direction arrow on the remote in order to pair it with the TT and that does speed things up considerably. A touch screen would be nice but then I'd be tempted to set it while driving along.

Thanks again, have a good weekend.

 

[dhn]

Thanks for the feedback. Glad things worked out for you.

 

[BigVan]

Having felt stupid for a few minutes I will say in my defense that searching for answers on the internet can lead to a lot of rabbit holes, garden paths, complicated procedures and red herrings, when the solution may be incredibly simple.
I read somewhere to upload easyGPSfix once a week. Is this something that people need to do really?

 

[Willy875]

Normally, your GPS stores information about the positions GPS satellites will occupy over the next 7 days.

It is essential that you update QuickGPSFix at least once a week.

 

[BigVan]

I did read that somewhere.
That means taking a laptop on a road trip and having an internet connection. Or an SD card to phone adapter?
I must admit it's not something I ever bothered doing, only when I bought new maps.

 

[Willy875]

If you download QuickGPSFix every week, your GPS will quickly calculate your position, even with a weak satellite signal.

 

[BigVan]

Probably a good thing to do then. Thanks for the advice.

 

[canderson]

Probably a good thing to do then. Thanks for the advice.

Here's how it works, in as non-technical and abbreviated a form as I can make it:

If it doesn't have one, your device picks up database information that is known as the 'almanac' from one of whatever available GPS satellites are visible when it first makes a satellite connection from a cold start. Worst case, the full almanac comes around approximately every 12-1/2 minutes. All of the GPS satellites keep a copy of this 'almanac' information, and it is typically updated from the ground every 24 hours or so to keep it ultra 'fresh'.

That data defines where all of the GPS satellites are expected to be found in the sky. Their location vs. yours, and the timing of the signals between them and you are what allows your device to do the math to determine your position. It's one huge triangulation project using signal timing with super precise clocks.

HOWEVER, satellites have this annoying habit of wandering about a bit in their orbits. The fancy phrase for that is 'orbital perturbation'. The Earth's gravity field isn't precisely uniform - heck, it isn't even really round - and then there's the impact of gravity from the moon, sun solar radiation pressure. GPS satellites aren't in low earth orbit, but those that are also have the slightest bit of atmospheric drag as well. Calculating all of that would be imprecise and a royal PITA, so instead, the almanac gets updated based upon where things are 'now'.

Anyway, a received almanac of 'ephemeris data', as it's known, goes stale after a while for reasons explained above. Known locations are less and less precise, and the calculation of your position becomes less and less precise as a result.

And here's the net result:

U.S. GPS Control Segment → authoritative orbit/navigation data → chip vendor's prediction service → TomTom server → download to your GPS receiver.

Rather than waiting however long to obtain a new almanac from a satellite every week or more, your computer can download this same kind of information (stored in both your PC and device in an 'ephem' or 'ephemeris' folder) and make use of it. TomTom and others obtain this information online from the GPS chipset manufacturers (SiRF, MediaTek or whomever) who provide this as a service for companies purchasing their hardware.

When your device wakes up, even from a cold start, if your ephemeris data is recent from TomTom, your device can make immediate assumptions about where the satellites are located, and give you a fast position fix.

 

[BigVan]

Thank you very much for the explanation. That is about as technical as I can handle without coming down with some 'Orbital perturbation' myself!
When you think of the enormity or it all, the technology, the infrastructure, the rockets and satellites, all the way to the box in your vehicle or pocket, it makes one feel quite humble. And a little guilty for getting angry when it all goes slightly off-course and sends one down a farmer's track. : )
Thanks again have a nice day.