Windscreen laminate blocking Satnav signal?

Ninap

I recently had the windscreen on my XC90 replaced, and subsequently found that my TomTom satnav intermittently began losing its GPS signal. I initially thought it was the Satnav that was at fault, and bought a new one (TomTom XL). That one worked at first, but now the same problem has emerged, whereby it will lose the GPS signal, and generally won't regain it. I'm assuming it's due to some type of anti-glare laminate that was put on the new windscreen, but why would the problem only happen intermittently? And why does my iphone have no problem picking up a GPS signal in the car?

Any advice/opinions v welcome....

Mr Benevolent

Fairly common issue on the XC90 after a quick Google, the windscreen has an IR blocking layer. The iPhone might be working better due to different circuitry, better signal, different software, different position in the car etc. The only thing I can suggest is testing the GPS in different positions.

Mr.David

As Confab said, probably the IR interlayer.

Yakuza

Might be best to get an external GPS antenna:
http://www.mp3car.com/gps/74584-volvo-xc90-antenna-module-for-gps.html

coylemj

Most windscreens of that type have an invisible rectangle somewhere that will permit high frequency radio signals to enter the car, you need this facility to use toll tags like EazyPass for the M50 and East Link.

It just may be possible to mount the GPS at a specific point on the dash or directly attached to the windscreen (via suction cup) to pick up signals. You say that the problem is happening intermittently which suggests to me that sometimes you get the positioning correct and at other times you don't.

See if your owner's manual mentions it, it may indicate where you need to mount a toll tag in the event that you have that particular windscreen, otherwise experiment and you may find that one particular spot on the dash will give you a decent signal.

Ninap

Posted query yesterday and then didn't get a chance to log in until today, so thanks to all for helpful comments/suggestions.

MrDerp

This won't solve your problem but:

Your iPhone doesn't have GPS, it has A-GPS. It doesn't connect to a satellite, rather it sends requests over the 3G network asking the network provider, whereabouts am I? The network quite easily detects your zone, and then the towers nearby assist in determining your 'exact' (and I use the term loosely) position. Your phones gyroscope then determines your direction.

dr.fuzzenstein

Confab wrote: »

Fairly common issue on the XC90 after a quick Google, the windscreen has an IR blocking layer. The iPhone might be working better due to different circuitry, better signal, different software, different position in the car etc. The only thing I can suggest is testing the GPS in different positions.

Isn't that infra red?
I don't think the GPS satellites work on IR signals, so an IR (or even UV) blocking layer should not have any effect.
On the other hand, if the screen is heated, the wire mesh within it could very effectively block any radio waves.
As for the laminate, it's simply plastic and should not have an effect on radio waves.

pete4130

As a surveyor, working with GPS every day...all it needs is a sight to sight signal. In cities, with taller buildings, or trees that tower over your car your signal can be interupted by signal multipath (signal bouncing off buildings/trees) and giving false readings.

The new window and recent issues might be causing some sort of problem though as a direct signal might be interupted?

Iphones work on triangulation rather than satellite GPS.

Man of Aran

Login to the TomTom website and assuming you have an account, hook up your XL via the USB.
There's a free patch to flashload that makes locating and latching to satellites easier.

It certainly improves it - I had a 340S XL bought in US last year and it was lousy until I flashed this patch recently.
Now excellent.

Ninap

Man of Aran wrote: »

Login to the TomTom website and assuming you have an account, hook up your XL via the USB.
There's a free patch to flashload that makes locating and latching to satellites easier.

It certainly improves it - I had a 340S XL bought in US last year and it was lousy until I flashed this patch recently.
Now excellent.

Thanks again. The problem is persisting. I moved the satnav to a different part of the windscreen and initially it worked fine. But on a long drive yesterday the gps signal went after an hour or so and then would not return. I tried switching on and off a few times but no luck. And I did have the unit updated with the latest software. Frustrating!

coylemj

pete4130 wrote: »

Iphones work on triangulation rather than satellite GPS.

iPhone has GPS, iPod Touch does not.....

iPhone pinpoints your location quickly and accurately using a combination of GPS, Wi-Fi, and cellular towers.

See 'Find Yourself' paragraph here.....

http://www.apple.com/iphone/built-in-apps/maps-compass.html

impr0v

coylemj wrote: »

Most windscreens of that type have an invisible rectangle somewhere that will permit high frequency radio signals to enter the car, you need this facility to use toll tags like EazyPass for the M50 and East Link.

On my car this is up around and behind the rear view mirror. It's not a Volvo, but it might be worth trying placing it up there, if that's feasible.

coylemj

MrDerp wrote: »

This won't solve your problem but:

Your iPhone doesn't have GPS, it has A-GPS. It doesn't connect to a satellite, rather it sends requests over the 3G network asking the network provider, whereabouts am I? The network quite easily detects your zone, and then the towers nearby assist in determining your 'exact' (and I use the term loosely) position. Your phones gyroscope then determines your direction.

What you're describing is called triangulation by cellular networks which is not the same as A-GPS. Anything which mentions GPS involves receiving signal from the GPS satellites. iPhones use A-GPS which is the use of GPS satellites augmented with GPS data supplied over the network.

A-GPS is 'assisted GPS' whereby the device gets additional data about the current status of GPS satellites using the 3G or GPRS network, this allows it to get a faster position fix and means it already has almanac data about the GPS satellites before it starts to calculate position using the data received from the GPS satellites which are visible.