I have a NAVMAN and a GARMIN sat navs - and both, when tested in two Z's showed the Z's digital readouts a tad over 2 kph fast.
That's pretty accurate - my Ford's 10 over!
2 kph is just a nice margin for safety.
Just fyi.

FROZZTY

 

It's pretty obvious on my Z...the digital readout is 2km off from the console analogue readout.

I use the digital one mostly as it keeps me free from Gov. Corporation!

 

Have checked mine several times on those dodgy overhead speed checkers on various freeways. Between 100 and 115 kph the radar showed 3-4 kph less than my speedo.

I wonder how accurate those things are. Someone told me they were probably more accuate than the hand held radars. Anyone know anything about this?

 

Thats good to know, yeah 2ks is a nice little cushon.

Good find!

But... I dont know about the acuracy of the GPS system. I think its only accurate to within a 5 foot radius or some number like that. So if theres a 5 foot area around the car, surely that would leave some error in the actual speed your going? Just a thought?

 

My sat nav varies between 0 and 5 metres out.
Maybe depending on how many sateillites are available.

Least showing so far 3, most, 9. This shows on the screen.

Dunno if this is technically corrrect as I guess the minimum should be 2 to form a triangle....duuuuh I failed those exams!


3.5k diff in speed between car digital speedo and sat nav speed at 100kph,dig read is slower.

Steve