What is more reliable the speed on your car speed or the speed on the tom tom?

Answer 1

MMM... would I trust a (cost to the manufacturer) £2.99 analogue speedo with plastic gears and contrary to popular belief, has no longer got to be within + or - 10% of true speed any longer to comply with the UK Construction and Use regulations; or do I trust the speed worked out by a multi billion dollar system of satellites, governed by synchronous atomic clocks?

I think I will go for the atomic clock system.

It pinpoints your cars location to within 10 - 15 feet (judging by passing bridges etc. on TomTom) at 100mph, which by my quick reckoning, 100mph is close on 147 feet per second. That's pretty accurate measuring.

Answer 2

The TomTom.
Car speedos by law may be perfectly on the right speed or up to 10% under (they cannot be over i.e. tell you you're going slower than you are). Speedos in cars work by having a sensor somewhere along the transmission of the car. This can therefore be affected by other factors (such as changing the total radius of wheels/ tyres). Bigger radius of wheel/tyre combination would make the car go slightly faster as would act in the same way that a gear does (based on a specific car).

The TomTom uses GPS (global positioning system). This means it measures how far you are moving in relation to time- so is more accurate.

If in doubt, always believe the one that is reading the highest- don't want to be caught speeding!

Answer 3

your car probably. tom tom takes an average speed between GPS nav points so it's not 100% reflective of true moving velocity. also there is some lag on the display and processing of data in a tomtom or other GPS, while your cars speedometer has a much faster response time. although if you have an old car or truck with lifted tires, or your tires are not properly inflated your speedometer could be showing an incorrect speed.

Answer 4

I would say if you had really good rhythm like me, the speed on the tom tom. I've know people that can keep an extremely high rate of speed going for hours. More fun too, keeps the party going.

Answer 5

Good question - I dont know the answer but my Tom Tom quotes my speed at about 3 or 4 MPH slower than my speedo - is yours the same?

Answer 6

Tom Tom, though there may be a small time lag because of the updating factor involved in the satellite signal reaching your sat nav.

If your car speedo is out of calibration (and they usually are) it will always show the incorrect speed.

I think the police allow for this known inaccuracy in car speedos.

Answer 7

The Tomtom.

Car speedos (If worn) are made to be a little bit over to allow for a margin of error. Try going past one of those speed trap things that tell you your speed. It'll always be a little less than your car says.

Answer 8

I would say the Tom Tom. Car speedo's are known to be innacurate, hence the 'leeway' under the speeding laws.

Answer 9

Let's see.. It's a choice between

1) relying on your speedometer that's physically linked to your car, and sole purpose and design is specifically to gauge your car's speed, or

2) rely on a piece of kit that's designed by a third party that relies on signals from satelites many miles in earth's orbit and a piece of software written by a completely different company that from time to time have been known to direct people through rivers, the wrong way up a one way street, along railway lines and off cliffs.

Difficult one isn't it?

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I can just imagine all sorts of people out there driving down the motorway with their eyes alternating between the speedometer and the satnav screen and trying to prove a point of one being better than the other. Just watch the road and you'll be better off than agonising about that 10% margin of error.

Answer 10

Car