longdog
Active Member
Some vehicles have to have a speedometer that is within 2%, calibrated before use when new, tested every 2 years, and recalibrated every 6 years. The speedos on these vehicles read the same as my ancient tomtom one new edition.
What vehicles are these. Police vehicles?
I have my satnav set up to give audible warnings at 105% of the speed limit. Lady voice says 'You are exceeding the speed limit" and it is spot on with what the dial says on a truck's calibrated speedo. To me that would indicate satnavs are quite accurate on speed calculations. My girlfriend hates using it as the lady voice speaks to her far more often...
longdog
Active Member
Any vehicle that is fitted with a tachograph, which can include Land Rovers.
Nodge68
Well-Known Member
From memory satnav speed calculations are based on the dopler shift principle. This should be very accurate to 1 or 2 % tolerance.
My Discovery 3 speedo reads 1 Mph faster than my satnav speed indication is showing at 70. Suggesting that the modern LR speedo is calibrated very accurately indeed.
The altitude displayed on my nav isn't always accurate as yesterday, on the M27 it showed the car at -12ft for a few minutes. I know the Discovery can wade but I'm sure it will struggle in 12ft of water!
My Discovery 3 speedo reads 1 Mph faster than my satnav speed indication is showing at 70. Suggesting that the modern LR speedo is calibrated very accurately indeed.
The altitude displayed on my nav isn't always accurate as yesterday, on the M27 it showed the car at -12ft for a few minutes. I know the Discovery can wade but I'm sure it will struggle in 12ft of water!
Irishrover
Well-Known Member
I'm reading this post from the sidelines. My TomTom also reads about 5mph slower than the speedo on my 2002 TD4,fitted with the standard LR 16" wheels, at 70 mph on the speedo. The F/L has the factory option of 15 or 16" wheels and I am sure that LR do not have specific speedo's on the production line for either option. Maybe they play it safe and fit a standard speedo designed to read "Slow".
If I am using the satnav, I tend to take it's speed reading as gospel.
If I am using the satnav, I tend to take it's speed reading as gospel.
englishbullterrier
Active Member
In every car I have ever owned, the speedo has indicated faster than the actual speed, measured by GPS. I think this is done to assist in not getting a speeding ticket !
