Adam_BlackRS

Borrowed my mates Road Angel Sat Nav and noticed the speed on the GPS wasn't reading what my car was saying.

Just wondering how accurate GPS speed is ?

CharlieSaff

I thought it was meant to be spot on!

vikingboy

AFAIK - its measured by doppler shift of the GPS signal so should be very accurate....99.9%?

Rick

VERY accurate mate. Much more than ur speedo.

Big Will_

Its been commented on for years that speedos are inaccurate to around 10%.

Normally they're "ok" at around 50mph - but either side of that they tend to over-read.

Which is handy when you go through a GATSO and look at your speedo as you see it and your needle's sat just over 30

RS500/364

DRIVE YOUR CAR AT HALF SPEEDO
120 DRIVE 60
SEE WHAT THE GPS IS AND THEN SORT YOUR SPEEDO SO IT IS RIGHT

Fiecos Dan

my 'Snooper' = 135mph, and on PF timing gear i was doing 133mpg.

My brothers 'Angel' = more accurate.

St3V3_C

GPS is spot on, but there is a delay if accelerating. You need to be at the same speed for a few seconds and then look at it.

Fiecos Dan

i was for 5 seconds.

but that will only work if the snooper/angel was under reading, not over reading.

dojj

iTrader: (3)

ours measures speed to 5 decimal places

but it's on the tracker

Rod-Tarry

Datron timing gear was 2mph faster than GPS monitor in car, my Stack speedo gave the same speed as Datron.