How fast am I going?

RoystonB · Occasional Visitor Joined: Aug 16, 2006 Posts: 19

Hi All,

This must have been asked before, but here goes. Embarassed

I have noticed that with the speedometer showing 70mph my TomTom 710 shows 65mph.

To get the TomTom to show 70mph the speedometer has to be registering in the region 76/77mph, which can be a little worrying if near the speed cameras.

So how accurate is the speed shown on the TomTom 710?

Many thanks, RoystonB 8O

zzr1200 · Posted: Tue Sep 19, 2006 2:20 pm Post subject:

The GPS is the accurate one. Car speedos generally have a bit of tolerance in them so that it reads slightly higher than you are actually going so that you don't get caught for speeding.

Different makes of car have different speedo accuracies as well. My BMW is extremely accurate upto about 100MPH (speedo says 100MPH, GPS says 99MPH), my wifes Renault speedo reads about 6/7% fast.

Hope that helps.

shauneco · Posted: Tue Sep 19, 2006 2:26 pm Post subject:

Not all car speedo's are 100% accurate usually a few MPH out either way, Also the TomTom's speed is reasonablly accurate on mine, It's a delayed reaction to the actual speed you're going, For this reason only take the speed on the TomTom as a very rough guide, You're cars speedo will be more reliable.

trog100 · Regular Visitor Joined: Sep 15, 2006 Posts: 195

i understand the satnav speed to be pretty reliable.. mine consistently reads 10% slower than my speedo..

i believe the satnav no question..

trog

Privateer · Posted: Tue Sep 19, 2006 2:40 pm Post subject:

Don't forget that your GPS speedo may be up to a second slow, i.e. if you have just started to accelerate, the GPS reading of the speed will be slow.

As long as you have been driving at a constant speed, in the same direction, on a level horizontal plane, for over a second then your GPS speed reading should be far more accurate than your vehicle's speedo.

Regards,
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pujro · Occasional Visitor Joined: Sep 17, 2006 Posts: 1

mine reads about 2 or 3mph higher than the car....so about 5% out.

Tim Buxton · Posted: Tue Sep 19, 2006 5:09 pm Post subject:

Green_ninja · Occasional Visitor Joined: Apr 27, 2006 Posts: 51

Car speedos have to read with in 10% at 30mph and 70mph and they MUST NOT underread, so the fac that your speedo is showing a faster speed is OK.

shauneco · Posted: Tue Sep 19, 2006 5:51 pm Post subject:

nmbaker

This is to stop you blowing the engine. On my Vecrtra SRi V6, it was set at 150mph. In Germany, I was showing 160 on the clock, GPS got to 150 and it felt like someone stamped on the brakes. I believe the GPS, but in stop/start traffic queues, I do not believe GPS or speedo, only ETA with approximation. BTW that was using a Garmin GPS12 with a Psion 5mx using TomTom RoutePlanner years ago. Nowadays, I do not go much over 120 as my job is not nearly as stressful and I have to do a lot more miles in a week than previously.

One nice feature you will find in the new version when you can buy it is that you can set to arrive at a particular time, so you know if you are on schedule or behind schedule. Is very handy if you have to arrive for appointments.

I know that if you had ETA displayed, it gave similar information, but this is better for me. Green on time - Red late
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