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PHILIP2908
Lifetime Member
Joined: Apr 03, 2005
Posts: 17
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 Posted: Thu Sep 18, 2008 12:29 am Post subject: Tom Tom speed accuracy |
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I've been using a basic TomTom ONE for the past 2 years and have always wondered about how the speed shown is about 5mph faster than that shown on the speedo of my Passat.
I'm told that GPS speed is more accurate and this was further reinforced by a recent holiday in the USA. With this the hire car was a huge, horrible 15mpg Dodge Charger (but at 55p per litre it wasn't that expensive to drive - £25 to fill it up!) and this had a GPS system that fed the satellite radio (wonderful) and also, I think, drove the speedo; as for the first time the speed shown exactly matched the speed shown on my TomTom that I took with me.
The question is: in the UK does anyone drive past speed cameras and through SPECS using the figures shown on the GPS system, or is the bog standard dashboard instrument the safest bet ??
I have never dared but I could be swayed by some stories of drive bys using the GPS speed shown and not got a ticket as a result ! |
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mikealder
Pocket GPS Moderator
Joined: Jan 14, 2005
Posts: 19638
Location: Blackpool , Lancs
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| Posted: Thu Sep 18, 2008 5:09 am Post subject: |
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| Welcome to the forum, go with the GPS speed reading it is far more accurate than the vehicles speedo, I only use GPS speed when on A roads and motorways, it is very handy for specs camera zones - Mike |
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M8TJT
The Other Tired Old Man
Joined: Apr 04, 2006
Posts: 10118
Location: Bexhill, South Sussex, UK
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| Posted: Thu Sep 18, 2008 8:21 am Post subject: Re: Tom Tom speed accuracy |
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| PHILIP2908 wrote: | | I've been using a basic TomTom ONE for the past 2 years and have always wondered about how the speed shown is about 5mph faster than that shown on the speedo of my Passat.! |
If this is really the case, (GPS usualy reads lower) then definitely go by the GPS. But I suspect your car spedo is actually reading faster than the GPS unless you have put oversize wheels/tyres on your car. They are required to by law to account for tyre wear etc., and if you follow your speedo you will be going faster than it indicates thus possibly speeding.
The various GPS specifications indicate a speed accuracy of somewhere near 0.1 mph , so even if you multiply this by a factor of 10, it is still far more accurate than the + 10 / -0 percent of the speedo. |
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TerryWalsh
Regular Visitor
Joined: Jul 29, 2005
Posts: 147
Location: Shrewsbury, UK
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| Posted: Sun Sep 28, 2008 12:23 pm Post subject: Tom Tom Speed Accuracy |
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I am pretty sure that the speedometer in American built cars is made to diffferent standards that those in Europe. Until last year I drove a US bulit Ford Focus and its speedo always agreed with my Navman Sat Nav. I now drive a European Mondeo and its speedometer always shows a higher speed than the same Navman unit.
Terry Walsh |
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PaulB2005
Pocket GPS Moderator
Joined: Jan 04, 2006
Posts: 9323
Location: Durham, UK
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| Posted: Sun Sep 28, 2008 7:10 pm Post subject: |
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Please don't ask questions multiple times. You already asked in this thread which has received 10 answers.
Posting questions multiple times means the same information is repeated on the forum and creates multiple answers.
Thread locked. |
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