Using a TomTom in a car with a heat reflective windscreen?

[jweaver]

When I got my TomTom (Palm Based wth external Bluetooth GPS) I had a VW Passat and it worked perfectly.

However, I recently changed my car to a BMW, which has a "heat reflective windscreen" and the GPS reception was awful.

I lived with it for a few day, but it was unworkable. So the solution for me was to put the Bluetooth Reciever on the BACK shelf and make up a 12V adaptor to keep it powered on permenantly.

This solution has served me well, but I now want some recent maps, which I can't get for the Palm version so my only option is to buy a 'standalone' version (i.e the TT One).

The problem is the front windscreen. I borrowed a colleagues and demonstrated that when its outside, I got full bars, but as soon as I moved it under the windscreen, the levels dropped.

On the BMW there is a 'cutout' around the rear-view mirror which doesn't hot have the 'coating' and if I put the GPS there, I get full strenght again.

The only thing I can come up with is to put an external GPS aerial up above the mirror, but the connection to the TTOne is going to be a nighmare, as it will be really fiddly to connect the power and aeria each time I insert/remove the TomTom.

- Do any of the standalone versions support my external Bluetooth Aerial (Which is working perfectly in the back of the car)?

- Do any of the TomTom units have a 'dock' which is connected to the Power/External areial allowing the Unit to be inserted/removed easily without disconnecting leads.


If anyone has any experience in this area, I am all ears.

I look forwards to your replies.

Jon

[mikealder]

Jon, You don't mention which type of GPS unit you are using, is it SiRF-III as most devices equipped with SiRF-III or the even newer Global Locate "Hammerhead" chipset work fine even under athermic glass.

If you are sure you will need the external aerial for the device you could take a look at the TomTom Go-x10 range (510, 710 or 910) these all have a separate mount to which you can connect an external aerial - Mike

[tonygold]

i have used my tomtom ONE europe in a friends 3 series bmw and the signal was totally unaffected by the windscreen. i'm sure it too had the heat reflective screen fitted and the signal was good. the ONE even picks up a workable signal indoors, although it does take longer to get a 'fix' on the signal initially.

[jweaver]

The GPS I am using now is the "TomTom Bluetooth GPS reciever" and it doesn't work under my windscreen.

I have been testing with a TomTomOne and it has exactly the same problem... If I put it outside of the car or in the 'clear' area around the rear-view mirror, its fine.. BUt as soon as I move it under the glass, the signal drops noticably.

Do any of the TomTOm units have the new type of GPS which will work under the glass. The TomTom ONE certainly doesn't work without a notable signal drop!

I can use an external aerial and put it in the 'clear' area, but this has to be connected to the TomTomOne each time I install/remove it from the car and this a little fidly.. Instead, I would like a 'dock' so that the conections are made easily.

I know that the TomTomOne cradle doesn't do ths, but what about the 510/710/910?

THe best solution for me would to have the TomTom 'sync' to my external Bluetooth aerial, but I am 99% sure that this feature isn't available..

I don't really know what to do, other than wait until my windscreen gets a stonechip and get it replaced with an 'uncoated' screen!

Jon

PS. I am with a friend now who is an "antenna designer" and has just bought a TomTom One.. He also has an 'external aerial' for me to try so I am going to go out and do a few tests.

WIth the TTOne, in order to get a perfect signal, I am SURE I will need an external Aerial and for the TTOne this isn't an option due to the fiddly imputs.. I will check out the x10 series to see if that mount will meet my needs!

[mikealder]

[jweaver]

Sorry. I missed that.. Are you saying that the 'dock' for the x10, has power/aerial inputs and the 'TomTom' simply snaps into it?

If so, I think that this is the route I might take..

Thanks for that.

Jon

[mikealder]

I hope this picture of my 910 mount answers your questions, it is quick release for the x10



Mike

[jweaver]

I have been able to do a bit of testing with a "TomTom One" today and am not sure what conclusion to come too.

If I put the TT1 on my dash board, I get a lock and a signal of about 50-60% for each satallite.

If I them move the TT1 to the cutout above the Rear-View Mirror, the signal goes up to between 95-100% and this is constant.. When I move the TT under the normal glass, the signal immediatly drops.


If I do the same with my original Bluetooth GPS, the results are pretty much the same...

I know from experience that my Palm (Running V5) and the Bluetooth GPS did not work at all well when the GPS was in the windscreen.. It was OK when there was a clear view of the sky, but as soon as I got between buildings, the accuracy dropped.

This is why I eneded up putting under the rear (uncoated) window..

The TT1 seems to be exactly the same as my Bluetooth GPS, so unless they have done something to make it more accurate when the signal is lower, I think I will have the same problem.

Next week I will borrow a colleagues TT1 for a few journeys to see what its like, but I think that an External Aerial is going to be the only option, which rules out the TT1 (And XL model) as its going to be too fidly to remove/insert the Aerial cable every day!

Its a shame that I can't get a Standalone TT to sync with my Bluetooth GPS.. If this was possible, I wouldn't have a problem.

I am still hoping taht someone out there has a BMW with the same glass as me and can comment first hand.

All the best

Jon

[jweaver]

I borrowed a TomTom ONE yesturday and as I expected, it wasn't very good.

Where as my Palm based TomTom (with the GPS under the back window) was flawless, the signal on the TT1 was very low.

When there was a clear line of sight, it was barely acceptable, but as soon as I moved into lanes, or areas with surrounding buildings the signal/number of satellites dropped. When this happened the map updates got sluggish and it would miss turnings and take a few 100ft to catch up.

So for example I would drive along a road, and then turn off.. TomTom would show me driving past the junction until it realised that I had turned off and a few seconds later would 'catch up'

This is exactly the same behavour which made me put my BlueTooth GPS under 'clear' glass, so I don't think that there is a solution to this, other than using an External Aerial.

But for the TT1, this is not practical for me, due to the way that it connects.. Its a shame as the TT1 is lovely and exactly what I want.. But with the windscreen that I have, its not practical for me!

Jon

[sollythegolly]

For information, and especially for people who are considering a purchase, I have recently purchased a TomTom ONE V2, which works absolutely fine under the athermic windscreen of my 03 reg Peugeot 406.

My previous PDA based version, however, which used an unbranded SIRF III GPS mouse, suffered from horrendous problems, and eventually, the mouse had to be banished to the rear of the car. This was really inconvenient, and the poor little sod was often left for days under pretty horrible environmental conditions (bake/freeze).

I gave up on it in the end, and splashed on the TomTom ONE. No probs so far.

[jweaver]

This doesn't make sense to me, as I just took my colleagues TomTom One (the new shape) out again to do a side by side comparison with my Palm (which BlueTooth GPS in the back of the car)

Where as my Palm was smooth and VERY accurate to me moving about.. The TomTom one was awful.. Still usable perhaps, but very jerky (and I am not talking about screen refresh, I mean that it was jumping about) and did not respond when I unexpectidly turned off for a few seconds.

The difference was like night and day.

I then repeated my test with signal strength and found that with my Bluetooth GPS (in the back) I was getting 80-90%. The TomTomONE was also giving the same when I put it in the un-coated space above the wing mirror.

But as soon as I lowered it under the coated section of the glass, the signal dropped to about 50-60% and started to fluctuate!


Perhaps the BMW coating has more of an effect than the Peugeot, but I can't see that, as I bet the windscreens are made by the same maufacturer!

Jon

[Darren]

Not sure why you are having this issue. We've tested current receivers such as SiRFStarIII, Nemerix and GlobalLocate Hamerhead in cars with athermic coatings and not had the issues you describe. Such symptoms were common with older designs but TomTom's current Bluetooth GPS is SiRFStarIII (the original was SiRFStarII) as was the original ONE so should work fine in such circumstances. Signal level will be lower because of the effect of the coating but they should still work properly.
_________________
Darren Griffin

[sollythegolly]

Well, all I can say is that my TT1 V2 sits centrally on its mounting at the bottom of the windscreen of the Peugeot, about as far as it can get from the side windows and the normal glass bits either side of the rear view mirror (which I believe are for attaching road toll tags/widgets so they can be auto-read), and have no problems whatsoever, Jon. The car is not fitted with a sun-roof, so no stray signals are entering via that route.

I keep it at the bottom primarily because the supplied mounting is next door to worthless, and by nearly sitting on the dashboard top, it doesn't have far to fall

[jweaver]

Well I am officially confused then.

The difference is night and day for me.. Even if I ignore the 'lower signal', the TT1 is no where near as accurate as my Palm when travelling about.

Perhaps its not as bad as my my Palm was when the , but its certainly worse than I hoped for.

As an example, I left the office at lunch time and took a 5 mile journey home (approx 5-10 mins) of which the majority was motorway.. But the time I had got home the TT1 still had not got a lock.

It was only when I stopped the car and gave it a change to lock on, it finally found its position.

This is more like what I used to get from my Garmin GPSIII 5 years ago!

Jon

[sollythegolly]

Jon, it very much looks like that not only do BMW make very fine cars, they also make very effective Faraday cages.

Hope you solve the problem - regrettably, I have no ideas.

Good luck

Jim

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