Sat Nav verus my Speedo

[10210ken]

I have had two different sat navs in three cars in every case the speed on the sat nav is about 5mph out compared to the speedo at about 80 mph. Which one is correct. THe speedo is the one which has the higher reading

Ken

[Phil Dicky]

10210ken said:

I have had two different sat navs in three cars in every case the speed on the sat nav is about 5mph out compared to the speedo at about 80 mph. Which one is correct. THe speedo is the one which has the higher reading Ken

Sat Nav will be right speedos are always out ranging form 5-10%

Phil

[droopsnoot]

SatNav is much more accurate at steady speeds. Under hard acceleration it can take some time for the GPS speed to 'catch up' as most commercial GPS receivers only send out updated data every second or two.

[bigdods]

GPS is the one to watch. Had my TVR tested for speedo accuracy on a rolling road - 100% accurate (yes I was surprised!) then checked TVR against SatNav at 30 and 60 both speedo and satnav agreed on the speed. Checked My Omega and Golf against Satnav both cars were over reading by a few percent as I would expect.

[arh]

The construction rules for cars say something along the lines of "a speedo must never read slower than the car is actualy traveling", therefore all speedos are built with a tolerence, normally 10%.

[kiticat0099]

I've tested the Road Angel against a Volvo V70, found the Volvo read 10% over against Road ANGEL; also tested against Seat Alhambra and was spot on.