How accurate are TomTom's?

jesta

jesta

jesta

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Joined
19 Dec 2004
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Hey,
was wondering the speed indicator on TomTom software,how accurate are they. Driving my Civic it says I'm doing 70 on the speedometer but on the TomTom it says 65.How accurate is the TomTom one?

Thanks.
 
Ah fair enough :)

Mine seems to be reasonably accurate, seems to be out by about 3-4mph at most speeds, haven't really tried above 80 odd though.
 
L0rdMike said:
Am I right in thinking that on large slopes GPS gets a bit funny and doesnt display your real speed?
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Yeh but the slope wont affect the GPS reading by a very large amount at all. Imagine if you were to look at yourself from a birds eye view moving horizontally beneith yourself going up a slope, you are infact travelling up the angled part of a triangle but you are looking at yourself moving along the straight line adjacent to the angle of incline.
 
Usually they're accurate to around 0.1mph - but this does vary upon conditions and manufacturer's spec. Some are more accurate (0.01mph for example).

According to one (seemingly outdated?) website:

Garmin's specifications quote 0.1mph accuracy but due to signal degredation problems noted above, perhaps 0.5mph accuracy in average automobile applications would be what you can count on.
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so should be accurate to within 1mph taking into account GPS variations and rounding of the speed

so if satnav says you're doing 80 and speedo says 85, the most you're doing is 81.
 
Ahhh right so its better to go with what the TomTom speed indicator then the speedo?
The past few times when I drive past a speed camera on the motorway and my speedo says 73(or so) and gps says 68mph I break a little just to make sure. :o
 
jesta said:
Ahhh right so its better to go with what the TomTom speed indicator then the speedo?
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I'd say no, following the GPS will lure you into a false sense of security. Momentary lapse in concentration, and you could get nicked.
 
So better to just use the speedo then?

Off topic,Gaijin I still haven't spotted your Civic driving around Brighton yet!
 
jesta said:
So better to just use the speedo then?

Off topic,Gaijin I still haven't spotted your Civic driving around Brighton yet!
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:eek: Must admit, havent ventured in that much what with the Christmas madness. Whereabouts do you live?

Its not in a state to be viewed at the moment anyhow, its rained pretty much every weekend and when it hasn't, i've been busy. Absolutely caked in crap.

Luckily work has decided to give us all a free valet today, so i wont have to do it!

Back on topic for a second, I generally go by speedo for safety, but do glance at the Tom Tom every now and again. Its not going to affect your journey time by that much going by the speedo, but it could save you some points and a bit of fuel!
 
i personally take note of how "out" my speedo is

if my speed says 30 im doing 28. You only get a ticket from a fixed speed camera at 10 % + 1 which is 34. So if my speed says 32 or whatever i know im actual fact only doing a real 30 and nowhere near the 35mph needed for a ticket so dont bother

so check your actual speedo, but just learn how "out" it is.
 
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When i fitted new dials I used my tomtom to "calibrate" the speedo.

Now, they are pretty much spot on.
 
MrLOL said:
i personally take note of how "out" my speedo is

if my speed says 30 im doing 28. You only get a ticket from a fixed speed camera at 10 % + 1 which is 34. So if my speed says 32 or whatever i know im actual fact only doing a real 30 and nowhere near the 35mph needed for a ticket so dont bother

so check your actual speedo, but just learn how "out" it is.
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I hear what you are saying but that 10% +1 is a guideline set out and it is completely up to the regional force what the tolerance is.

Not something to i'd want to risk, as the cars I aspire to own are typically group 20 and with an insurance premium to boot.
 
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