E63 COMAND thinks I'm in the north sea

[Peter DLM]

So I was returning from Calais on the Eurotunnel and all seemed fine until I disembarked in Folkestone and the car still thought it was in Calais. It worked fine going the other way!

As I drove home we ended up somewhere in the north sea 100 miles west of Felixstow.

I've done all the obvious things, except disconnecting the battery. Even performed a service tech reset using the secret menu.

Anything to try before I take it to the dealer?

 

[Alfie]

So I was returning from Calais on the Eurotunnel and all seemed fine until I disembarked in Folkestone and the car still thought it was in Calais. It worked fine going the other way!

As I drove home we ended up somewhere in the north sea 100 miles west of Felixstow.

I've done all the obvious things, except disconnecting the battery. Even performed a service tech reset using the secret menu.

Anything to try before I take it to the dealer?

Check the number of satellites the comand can see.

 

[Yugguy]

You have actually slowed the speed of the earth's revolution with the mighty torque of your engine and therefore all satnavs are reporting inaccurately.

 

[John]

I had this on my E55 - thought I was in the North Sea as well.

I thought it might be an aerial but turned out to be a disc-reading error.

Cleaned the disc and it worked fine after.

 

[Peter DLM]

Check the number of satellites the comand can see.

I couldn't see how to do this, I did look. It's a 2015 car with the hard disk based system.

You have actually slowed the speed of the earth's revolution with the mighty torque of your engine and therefore all satnavs are reporting inaccurately.

Hahah it's possible I guess :bannana::bannana:

I had this on my E55 - thought I was in the North Sea as well.

I thought it might be an aerial but turned out to be a disc-reading error.

Cleaned the disc and it worked fine after.

This system doesn't have a DVD disc anymore, it's all on hard disk afaik.

 

[Deleted member 6183]

You have actually slowed the speed of the earth's revolution with the mighty torque of your engine and therefore all satnavs are reporting inaccurately.

Not only that but he's managed to turn the earth around so East is now West.

Never mind the pollution this is a far more worrying development.

 

[Rashman]

Could very well be antenna failure.
Not uncommon.

 

[Peter DLM]

Not only that but he's managed to turn the earth around so East is now West.

Never mind the pollution this is a far more worrying development.

Hahah yes I realisey I typed west I stead of east, too late as Alfie had already quoted it.

 

[Yugguy]

The Core (2003) - IMDb

You'd best be getting some Unobtanium in.

 

[french]

The title is so funny...well done, hope you get it sorted soon.

 

[fraggles]

I find the sat nav in my e class pretty ropey too, nothing actually wrong with it, it just looses its way from time to time. It's not the best system to be fair

 

[daveenty]

Mine gets lost sometimes (same car as Peters) but I put it down to interference from masts or something (not that I've seen any)

Usually heading N bound on the M6 around Stafford way, it tells me that I'm up around Lancaster for some reason. No idea why, and it doesn't do it everytime, but to cure it I just set the thing and tell it to take me to my home address. This seems to sort it out, or has done so far...

 

[st13phil]

I couldn't see how to do this, I did look. It's a 2015 car with the hard disk based system.

It's on the page that shows the Compass and position coordinates. A little satellite symbol with a number next to it.

As well as GPS, COMAND uses dead reckoning to display your position to cover times when it temporarily loses a satellite fix, like when you're in a city travelling between tall buildings. This has the amusing byproduct that when you exit the Eurotunnel carriage, until the unit picks up a good satellite constellation, the map display plots your movements from where it last had a GPS fix. So you see yourself moving in Calais while you're really in Folkestone, or vice versa.

My guess is that your COMAND hasn't managed to get a satellite fix and has therefore continued to work in dead reckoning mode - hence it thinks you're somewhere in the North Sea. Checking the number of satellites it can see will either confirm or dispel this.

 

[st13phil]

Mine gets lost sometimes (same car as Peters) but I put it down to interference from masts or something (not that I've seen any)

Interference from masts or something, eh? It's probably gone deaf by the time you reach Stafford

 

[Peter DLM]

So, there is no number next to the little satellite image. I guess this means the antenna is dead. Pretty peculiar that it happened on the train.

 

[st13phil]

It could be / have been intermittent for a while with the dead reckoning covering it up.

 

[st13phil]

Now I'm at the PC instead of responding via the App on my phone, here's a slightly more elaborate explanation.

For a GPS receiver (GPSR) to work, because the signals involved are so tiny, it has to "know" where to look in the sky for the satellites. To do this it maintains an Almanac which tells it (roughly) where to look in the sky to find the satellites it needs, based upon it's position and the current time. The Almanac information regarding position of the satellites isn't actually that accurate, but it massively narrows the search area that the GPSR has to scan to find satellites. The almanac data is typically valid for several months.

To get an accurate position the GPSR requires Epheremis data which precisely describes the orbital position and clock correction information of a particular satellite. Each satellite broadcasts Almanac data for all satellites in the GPS system, while the Epheremis data is broadcast only by the satellite it relates to. Unlike the Almanac data, the Epheremis data is valid for only a short time (30 minutes).

So...

Once your GPSR can't see the sky for more than 30 minutes (i.e. a bit less time than a chunnel crossing) it has to resort to the Almanac data to find the satellites because the Epheremis data is out of date. But, to use the Almanac data it needs to know where it is, plus the current time, so it knows where to look in the sky for the satellites that will provide the Epheremis data that will allow it to resolve your position. The trouble is, that you've moved 25 miles or so from it's last known position (due to your chunnel journey), so it will be looking in the wrong place. At this stage, the GPSR resorts to carrying out a full scan of the sky to first collect Almanac data which will allow it to "lock on" to satellites and finally get the data it needs to resolve your position.

All this is a grossly simplified explanation of why, all the time your COMAND system managed to make even a poor job of "seeing" the satellites it needs, it could keep track of where you were. However, once it's real position differed from where it last knew itself to be (i.e. your chunnel trip) it then has resort to Almanac data - which means it may not be looking in precisely the right place to see the satellites. As the signals are so tiny, if the antenna is sub-par then the signal strength will not be high enough to overcome the fact that it's looking in slightly the wrong place. Ultimately it will resort to carrying out a full sky scan to find the satellites again. A sub-par antenna makes this a much slower process, or maybe an impossible one.

The answer is (probably) that you need the antenna replacing, but it could be an internal fault with the GPSR.

 

[Peter DLM]

"Slightly more elaborate".....

Thanks for typing out all that, fascinating, but I'm taking the stupid thing to the dealer.

 

[st13phil]

"Slightly more elaborate".....

Thanks for typing out all that, fascinating, but I'm taking the stupid thing to the dealer.

That's what I'd do

 

[Peter DLM]

So software flash failed, GPS antenna replacement failed, now replacing a/the COMAND control unit.

Quite how using the Eurotunnel caused this I have no idea. I'll try and find out if some chip fried itself or the firmware corrupted itself to the point where it couldn't be reflashed.