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PAUL-R-S Occasional Visitor
Joined: Jun 03, 2005 Posts: 39 Location: london, uk
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Posted: Sat Jan 07, 2006 2:11 pm Post subject: CURRENT SPEED |
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ive been using my ttn5 with the tomtom gps reciver for about 4 months now. ive noticed that the fast im driving the further out the speed thats being displayed is from my speedo. ive tried it in 2 different cars (both fords).
is anyone else having this problem and can it be relied apon ? |
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badgerdid Occasional Visitor
Joined: Dec 08, 2005 Posts: 41
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Posted: Sat Jan 07, 2006 2:19 pm Post subject: |
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Mine always seems to be 4 miles an hour less than my speedo says, this is with pda through bluetooth. |
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mikealder Pocket GPS Moderator
Joined: Jan 14, 2005 Posts: 19638 Location: Blackpool , Lancs
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Posted: Sat Jan 07, 2006 2:48 pm Post subject: |
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Paul, this topic has been covered before, the last time http://www.pocketgpsworld.com/modules.php?name=Forums&file=viewtopic&p=178074&highlight=#178074 although a search will reveal loads more, car speedos are well known to be inaccurate when compared to GPS, but you do need to be aware of the limitations, straight, flat roads offer the best speed data, other factors can mess up the GPS signal, but I would say trust it over and above the data from your cars speedo - Mike |
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PAUL-R-S Occasional Visitor
Joined: Jun 03, 2005 Posts: 39 Location: london, uk
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Posted: Sat Jan 07, 2006 4:13 pm Post subject: |
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cheers mike.
i went through a speed trap before xmas car said 55 and tt was saying 50.
not heard anything yet so fingers crossed will be ok |
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lupos0_1 Lifetime Member
Joined: Sep 08, 2005 Posts: 765 Location: Berkshire
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Posted: Mon Jan 09, 2006 9:33 am Post subject: |
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Speed Camera Database?? _________________ -------------------------------------------------------
Nokia N95
McGuider V7
Latest Maps
(Internal GPS) |
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martike Regular Visitor
Joined: Aug 02, 2005 Posts: 194
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Posted: Mon Jan 09, 2006 1:49 pm Post subject: |
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It’s very easy to check the accuracy of your speedometer : drive at a set speed on a road with distance markers, check the time it takes to cover a certain distance, calculate your speed, then check it against your speedometer reading.
It’s not unusual for the speedometer error to be as much as 8 or 10% and it usually overstates your true speed. |
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peterc10 Frequent Visitor
Joined: Aug 21, 2005 Posts: 1761 Location: Kent, England
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Posted: Mon Jan 09, 2006 4:29 pm Post subject: |
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The easier way is to use your sat nav. As long as you are doing a constant speed on a reasonably straight and level road it will be right to within a gnats whereas your speedo could be out by up to 10%. It is certainly more accurate than pressing stopwatches when yoy pass markers in approximate positions. |
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martike Regular Visitor
Joined: Aug 02, 2005 Posts: 194
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Posted: Mon Jan 09, 2006 5:22 pm Post subject: |
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Checking your GPS by comparing it with a speedometer which has been checked by comparing it with GPS doesn’t make a lot of sense. You need an independent method, and a good old time/distance/speed manual calculation is a very easy way to do it (within certain limits of accuracy). |
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julianbarker Lifetime Member
Joined: Apr 12, 2005 Posts: 431
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Posted: Wed Jan 11, 2006 1:06 am Post subject: |
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The time/distance/speed calculation is what your GPS is doing. It is doing it several times a second and giving you the averaged results - which is why it is pretty accurate. The reason why roads that are not flat or straight induce errors is because they affect the averaging of movement across the geoid used in the GPS calculation. Also, becasue it is an average, if yo uare changing speed, the average will not show your current speed. Even so - most GPS figures will be lots more accurate than a speedo in most situations. |
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gnattycole Occasional Visitor
Joined: Jan 12, 2006 Posts: 3
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Posted: Thu Jan 12, 2006 11:19 pm Post subject: |
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I find that UK/European cars tend to over read the speed after about 45mph. Every time I drive in the USA car speedos seem spot on to the single unit there. I think it's a ploy to let folk think they're doing 80 when they're in fact doing the motorway limit in the UK. Keeps the plods happy I suppose. |
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mav36 Occasional Visitor
Joined: Dec 06, 2005 Posts: 3
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Posted: Thu Jan 12, 2006 11:28 pm Post subject: Showing speed |
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Hi guys,
I have both tt300 and tt5 for pda - i don't recall it ever showing my speed!! is there some thing i need to do to either for it to show my speed,
I am fairly new to all this sat nav stuuf, sorry if its an obvious or stupid question |
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mikealder Pocket GPS Moderator
Joined: Jan 14, 2005 Posts: 19638 Location: Blackpool , Lancs
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Posted: Fri Jan 13, 2006 12:29 am Post subject: |
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Mav36, for TTN5,x go to preferences then status bar preferences (use the RH arrow to get to it) then tick the speed check box and it will display speed in the lower RH corner of the display when in use - Mike |
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mav36 Occasional Visitor
Joined: Dec 06, 2005 Posts: 3
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Posted: Fri Jan 13, 2006 11:43 pm Post subject: |
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Mike,
Thanks for the advice, will give it a go and let you know how I do,
once again,many thanks |
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Robin2 Lifetime Member
Joined: Nov 24, 2003 Posts: 1441 Location: Swansea
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Posted: Sat Jan 14, 2006 8:18 pm Post subject: |
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European Construction and Use regulations make it obligatory for new car speedos to be between 0 and 10% fast. This means that most car makers pitch it somewhere near the middle of that range to allow for manufacturing tolerances.
Robin _________________ TomTom One v3 Europe, Navcore 7.903, Western Europe 835.2420
TomTom Go 720 Europe, Navcore 8.351, Western Europe 855.2884
Satmap Active 10
Plus a lot of other PDA GPS kit, seldom used |
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cfalz Occasional Visitor
Joined: Jan 17, 2006 Posts: 4
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Posted: Tue Jan 17, 2006 1:43 pm Post subject: TomTom speed accuracy |
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My TomTom reads a couple of miles slower than the speedometer in my car. That is consistant with the portable radar signs that I pass periodically that the police put out to remind you of how fast you are going. I've been impressed with the accuracy of the gps speed rating. :D |
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