TomTom SatNav + VW-Golf speedometer

[mixer]

My mate uses his Tomtom in his works vehicle which has a fitted tachograph - the speed on his Tomtom shows exactly the same as the speedo in the van at all speeds. When he uses the Tomtom in his own car the car speedo always shows him going a little bit faster than indicated on the Tomtom.

Yes i think this sounds very likly becouse i drive a coach and i no my tachograph has to get Re-calibrated every year or so, and its limited to 100k or 62MPH so next time im in my coach on the motorway i will test it in there and check it with my TomTom speed and report back

[Ghoulie]

road side speed readers are never reading the same speed as my vehicle - whether it is by my speedo reading or sat nav reading

ergo - they are not calibrated accurately - one at my speedo at 30 says I am doing 33 mph - its cousin at the opposite end of the road says 28 mph at my speedos 30

my sat nav at 30 mph is a speedo reading of 33 mph

If you read any of the sat nav forums - there are very good reasons / arguments to beleive your sat nav.

A recent case where a van driver was fitted up for doing 60 mph in a 50 mph zone by plod was so sure he was not speeding ( and fear for his driving job and points on his licence) mentioned it to his boss. Unknown to the driver - all the works vans were fitted with a satnav (Navman) based tracking device so they could see what drivers were up to. The boss got hold of Navman and gave them the spiel and asked if there was anything in their tracking system records that could prove a particular speed the vehicle was driving at.

Fortunately for the driver they could - they took it to court - Navman guy produced as expert witness and proceeded to show the evidence from the trcaker records that proved he wasn't speeding at all - 47 mph from memory. Another account of this incident is reported here :-

_http://www.pocketgpsworld.com/Van-driver-uses-GPS-data-to-beat-speeding-fine-8505.php

[mixer]

I have just tested my TomTom with the coach i drive (a Bova) and the speed on the coach was 100K or 62MPH and the satnav speed was reading 61MPH so i put the 1MPH down to tyre wear, so i would think the TomTom is the most accurate reading, strange but true

[carshalton]

Unless you are going along a road lined with trees or in a tunnel.The sat nav is more accurate.

[mjn]

Gave up with TomTom on my pda a long time ago. Now use McGuider and you can set the SavNav speed plus or minus to match your car Speedometer. The speed alarm goes off exactly as per your speedo.

[noff]

Well had a to drive up the M1 today and my golf was saying 75 when my tomtom was 71.

[mixer]

Well had a to drive up the M1 today and my golf was saying 75 when my tomtom was 71.

It must be a golf thing M8 i looked at my speedo today in my townCenter and whent past a radar what flashes ye speedo up and my speedo was saying 41mph but the radar was saying 40mph, So it seams the faster i go the more inaccurate the speedo becomes, i did not have my satnav this time to check the speed on that but no dought it will of been a diffrent reading again