Why do some cars block GPS signals?

Jez · 28 Aug 2009 at 12:13

Does anyone have any idea why some cars seem to block GPS signals from entering? It is beginning to bug me somewhat.

Admittedly i have not a huge sample to go on, the only cars i have experienced no GPS have been a Bentley Flying Spur and both the old and new gen Mercedes S-class. I am also told by a friend that the M5 seems to block GPS too.

Solve this for me people

PardonTheWait · 28 Aug 2009 at 12:14

Isn't it just the coating on some windscreens?

thecremeegg · 28 Aug 2009 at 12:16

Surely these cars have built in satnav so you dont need extra GPS

iaind · 28 Aug 2009 at 12:17

PardonTheWait said:
Isn't it just the coating on some windscreens?

Yup, UV coating. Most cars have a small gap in the coating in the middle of the windscreen for that purpose though

NVP · 28 Aug 2009 at 12:17

It is to do with the heating elements in the windscreens I think... I'm assuming they cause some sort of interference with the signal making it harder for the GPS device to locate and lock on. I used to have this problem in my Dads Volvo, I normally got the GPS signal by holding it out of the window until it locked and then it would have enough satelite connections to be able to work inside the car.

EDIT: Oh is it a UV coating? I just assumed it was the heating elements... but yeah some cars do not have them so I guess the a UV coating is more plausible...

Dogbreath · 28 Aug 2009 at 12:18

Heated windscreens don't help, but many windscreens now have a solar control coating to reduce the sun heating the car up. These are metallic and very effective at blocking high frequency radio.

iaind · 28 Aug 2009 at 12:19

nuvpal said:
It is to do with the heating elements in the windscreens I think... I'm assuming they cause some sort of interference with the signal making it harder for the GPS device to locate and lock on. I used to have this problem in my Dads Volvo, I normally got the GPS signal by holding it out of the window until it locked and then it would have enough satelite connections to be able to work inside the car.

EDIT: Oh is it a UV coating? I just assumed it was the heating elements... but yeah some cars do not have them so I guess the a UV coating is more plausible...

My car has heating elements but no coating - GPS works fine

DrDee · 28 Aug 2009 at 12:21

Worst "I have been in nice cars" thread ever

iaind · 28 Aug 2009 at 12:25

DrDee said:
Worst "I have been in nice cars" thread ever

Some Clios have UV coatings - I wouldnt consider a Clio a "nice" car

Jez · 28 Aug 2009 at 12:29

DrDee said:
Worst "I have been in nice cars" thread ever

Oh do go away, those are just a couple of cars i happened to have noticed it in, i would simply be interested in knowing why some cars seem to almost completely block GPS, whereas others don't affect it at all.

Its not a problem as such as you'd always use the built in GPS anyway, but it does mean that you cant use for example an iphones position facility for traffic and all that sort of stuff. More to the point, i just want to know the technical reason as it seems random whether you'll get GPS or not.

iaind · 28 Aug 2009 at 12:31

What cars have you noticed it in?

Jez · 28 Aug 2009 at 12:31

Dogbreath said:
Heated windscreens don't help, but many windscreens now have a solar control coating to reduce the sun heating the car up. These are metallic and very effective at blocking high frequency radio.

I assume that this coating is also likely to be found on all the other windows too? Hence the almost total lack of GPS in the S's and the Bentley regardless of position in the car?

Explains the problem anyhow

As this becomes more and more common (if indeed it is) then this is going to surely cause quite a problem for users of portable satnav's?

NVP · 28 Aug 2009 at 12:38

Is it plausible to get an external ariel that can recieve the signals and pass them (through an internal cable) to the sat-nav?

In the future do you think they will be able to modify the coating somehow so as to not omit the required fequencies?

PardonTheWait · 28 Aug 2009 at 12:41

I don't remember what car it was in but I've definitely been in one where it wouldn't work on the windscreen but did work on the side window. Bit awkward, but it worked.

Father Ted · 28 Aug 2009 at 12:41

iaind said:
What cars have you noticed it in?

Jez said:
... the only cars i have experienced no GPS have been a Bentley Flying Spur and both the old and new gen Mercedes S-class. I am also told by a friend that the M5 seems to block GPS too.

iaind · 28 Aug 2009 at 12:45

Father Ted said:

*grumblegrumble* pah...

clv101 · 28 Aug 2009 at 12:49

Dogbreath said:
Heated windscreens don't help, but many windscreens now have a solar control coating to reduce the sun heating the car up. These are metallic and very effective at blocking high frequency radio.

Exactly this, likely not just on the windscreen but on all glass. I bet your cell phone performance is poor too. It's the same kind of stuff they put on the new Virgin Voyager and Pendolino trains which knocked out the cell phone coverage.

Howard · 28 Aug 2009 at 12:50

Yeah my old Megane had a reflective coating that played havok with the GPS signals, was a real annoyance!

DrDee · 28 Aug 2009 at 12:52

Jez said:
Oh do go away

Trolled bro, trolled.

or you know, L2takejoke.

Jez · 28 Aug 2009 at 12:53

clv101 said:
Exactly this, likely not just on the windscreen but on all glass. I bet your cell phone performance is poor too. It's the same kind of stuff they put on the new Virgin Voyager and Pendolino trains which knocked out the cell phone coverage.

If this spreads to cars not equipped with GPS this is going to become a bit of a problem.

Weirdly, cell phone reception seems absolutely fine in everything :confused: