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Mark_W Occasional Visitor
Joined: Jun 09, 2005 Posts: 10 Location: Devon, UK
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Posted: Mon Mar 31, 2008 3:55 pm Post subject: TomTom Go GPS MPH |
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I still got my old trusted TomTom Go 300. Travelling back from Leeds to Devon this weekend, I notice that the GPS speed was 5 MPH faster than the Cars MPH.
The car is a 3 month old Ford C-Max, so which is correct, the cars MPH or the GPS MPH.
I look forward to the replies,
Mark |
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dhn Frequent Visitor
Joined: Oct 08, 2007 Posts: 2544 Location: Toronto CANADA
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Posted: Mon Mar 31, 2008 4:01 pm Post subject: Re: TomTom Go GPS MPH |
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Mark_W wrote: | I still got my old trusted TomTom Go 300. Travelling back from Leeds to Devon this weekend, I notice that the GPS speed was 5 MPH faster than the Cars MPH.
The car is a 3 month old Ford C-Max, so which is correct, the cars MPH or the GPS MPH.
I look forward to the replies,
Mark |
The GPS. There is a thread here somewhere that goes on for many, many pages about this issue. |
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tgold Regular Visitor
Joined: Nov 07, 2004 Posts: 98 Location: UK or USA from time to time.
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Posted: Mon Mar 31, 2008 4:21 pm Post subject: Re: TomTom Go GPS MPH |
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Mark_W wrote: | I still got my old trusted TomTom Go 300. Travelling back from Leeds to Devon this weekend, I notice that the GPS speed was 5 MPH faster than the Cars MPH.
The car is a 3 month old Ford C-Max, so which is correct, the cars MPH or the GPS MPH. | If you are correct, that the car speedo was indicating LESS than the GPS then you should get the speedo replaced under the warranty as it is defective. Or were you confused and the speedo was showing 5mph more than the GPS, which is quite normal.
Tony |
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Border_Collie Pocket GPS Verifier
Joined: Feb 01, 2006 Posts: 2543 Location: Rainham, Kent. England.
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Posted: Mon Mar 31, 2008 4:35 pm Post subject: |
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Quote: | I notice that the GPS speed was 5 MPH faster than the Cars MPH. | By law the cars speedo can over read by up to 10% but must NOT under read.
So, e.g. if you are doing a true 50 mph your speedo can read as high as 55 mph. (50 +10% = 55) but must NOT read 49 or under.
The GPS will be accurate if you are driving at a steady speed along a straight level road. _________________ Formerly known as Lost_Property
And NO that's NOT me in the Avatar. |
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forky Lifetime Member
Joined: Sep 18, 2005 Posts: 277 Location: Helston
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Posted: Mon Mar 31, 2008 5:50 pm Post subject: Re: TomTom Go GPS MPH |
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dhn wrote: | Mark_W wrote: | I still got my old trusted TomTom Go 300. Travelling back from Leeds to Devon this weekend, I notice that the GPS speed was 5 MPH faster than the Cars MPH.
The car is a 3 month old Ford C-Max, so which is correct, the cars MPH or the GPS MPH.
I look forward to the replies,
Mark |
The GPS. There is a thread here somewhere that goes on for many, many pages about this issue. |
The Thread is here:
http://www.pocketgpsworld.com/modules.php?name=Forums&file=viewtopic&t=63445&highlight=gps+speed _________________ Garmin Nuvi 2699lmt
Samsung Galaxy S9 (o2) contract |
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tgold Regular Visitor
Joined: Nov 07, 2004 Posts: 98 Location: UK or USA from time to time.
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Posted: Mon Mar 31, 2008 6:39 pm Post subject: |
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Lost_Property wrote: | Quote: | I notice that the GPS speed was 5 MPH faster than the Cars MPH. | By law the cars speedo can over read by up to 10% but must NOT under read.
So, e.g. if you are doing a true 50 mph your speedo can read as high as 55 mph. (50 +10% = 55) but must NOT read 49 or under. | Under EC Community Directive 75/443(97/39) the maximum positive error is 10% plus 4km/h which comes out to a maximum permitted displayed speed close to 57.5 mph in that example.
Tony |
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D4VE Lifetime Member
Joined: Aug 31, 2005 Posts: 207 Location: Hertfordshire
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Posted: Mon Mar 31, 2008 7:08 pm Post subject: |
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And how frustrating is it when everyone in front of you is going at 50 MPH through a series of SPECS and you can only travel at 45 MPH (TomTom speed)
Dave |
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Border_Collie Pocket GPS Verifier
Joined: Feb 01, 2006 Posts: 2543 Location: Rainham, Kent. England.
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Posted: Mon Mar 31, 2008 8:32 pm Post subject: |
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Quote: | Under EC Community Directive 75/443(97/39) | I'm still English at the moment, I'm putting off becoming European until the day I die.
On a more serious note, how can the directive relate to us and MPH when it shows 10% +4km/h, there's no such thing as km/h in England or has the Britsh Law on Imperial measurements been repealed under some other EC Directive? e.g. up-u-2-brits. _________________ Formerly known as Lost_Property
And NO that's NOT me in the Avatar. |
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uffe73 Frequent Visitor
Joined: Jul 23, 2004 Posts: 521 Location: Sweden
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Posted: Mon Mar 31, 2008 8:48 pm Post subject: |
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Lost_Property wrote: | Quote: | Under EC Community Directive 75/443(97/39) | I'm still English at the moment, I'm putting off becoming European until the day I die.
On a more serious note, how can the directive relate to us and MPH when it shows 10% +4km/h, there's no such thing as km/h in England or has the Britsh Law on Imperial measurements been repealed under some other EC Directive? e.g. up-u-2-brits. |
Maybe it's about time that the brits adapt to the rest of Europe...? |
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john877 Lifetime Member
Joined: Mar 16, 2007 Posts: 468
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Posted: Mon Mar 31, 2008 9:16 pm Post subject: |
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my car speedo is about 5 mph faster than the sat nav which in a way is a good thing as it allows you a little margin of error
I am sure I have read it somewhere that the sat nav are more accurate than the speedo because it tracks you with a GPS signal |
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SatMonkey Lifetime Member
Joined: Nov 11, 2007 Posts: 45
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Posted: Mon Mar 31, 2008 9:16 pm Post subject: |
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D4VE wrote: | And how frustrating is it when everyone in front of you is going at 50 MPH through a series of SPECS and you can only travel at 45 MPH (TomTom speed) |
Well I'm glad it's not just me that finds that really annoying! |
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shadamehr Banned
Joined: Apr 25, 2006 Posts: 507
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Posted: Mon Mar 31, 2008 10:59 pm Post subject: |
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The points are all covered in the thread linked to higher up.
But as it is a long thread, I will summarise the main relevant points in terms of what has been mentioned in this thread itself:
1) Speedometer can (and usually is) higher than the actual speed, but as stated MUST NOT be lower than true speed.
2) GPS indicated speed, is correct to around 0.5mph of actual speed (that is less than half of a single mph out - that's pretty darned accurate!)
3) The other thread talks long and hard about the effects of going up a hill, down a hill etc, rather than travellling a flat road in relation to the effect this will have on the gps' ability to correctly report speed. Some clever readers actually calculated however that as the maximum permitted gradient under law is of a certain value, then even allowing for travelling the steepest road in the country, this would have an all but negligible effect on the gps reported speed, and thus accuracy, in real terms.
4) You can therefore be safe in the knowledge that your gps reported speed should be highly reliable.
Hope that helps, but if you can wade through it, the other thread makes for interesting reading in places. |
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Mark_W Occasional Visitor
Joined: Jun 09, 2005 Posts: 10 Location: Devon, UK
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Posted: Tue Apr 01, 2008 10:36 am Post subject: |
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Thanks for the replies,
If what is being said that the speedometer can read over rather under, then technically if the car speedometer is reading at 70mph I am doing 75mph I am breaking that speed limit. The readings I gave were with the Cruise control, on the straight level road of a motorway with full sat connection via TomTom aerial.
I have got mates at the dealership, I think I will take the workshop Forman out with the TomTom connected to see what he says, I thought I read somewhere that the GPS speed was accurate, I wonder how many other new cars on the road are given the same reading as mine.
Re D4VE reply, yes your right, I couldn’t understand why everyone was over taking me on a Spec part of the motorway, I then set the cruise control to the speed showing on the TomTom.
Thanks for the replies.
Mark |
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Darren Frequent Visitor
Joined: 11/07/2002 14:36:40 Posts: 23848 Location: Hampshire, UK
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Posted: Tue Apr 01, 2008 10:44 am Post subject: |
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Mark_W wrote: | Thanks for the replies,
If what is being said that the speedometer can read over rather under, then technically if the car speedometer is reading at 70mph I am doing 75mph I am breaking that speed limit. |
No. you misunderstand. If the speedo reads 'over' then it shows 70mph when your true speed is 65mph.
If it read 'under' (which is prohibited) then it would indicate you were going slower than you actually were. _________________ Darren Griffin |
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Mark_W Occasional Visitor
Joined: Jun 09, 2005 Posts: 10 Location: Devon, UK
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Posted: Tue Apr 01, 2008 10:59 am Post subject: |
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Hi Darren,
My car speedo is reading under by 5mph on the GPS speed reading, so if I drive by the car speedo and increase the car speed to show on the car speedo 70mph, the true speed (by the GPS) will show I am doing 75mph.
Mark |
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