How accurate

[kiwi]

Depends how close together those two points are!

It's interesting how some people assume a sat nav is always correct... a bit like the general assumption that a digital display is more accurate, especially if it has lots of decimal places.
Anyone got (or can lay hands on) more than one sat nav? You could drive along and get a passenger to compare the displayed speed.

Correct

There is a delay that is visible if you look with a dramatically chaging speed (heavy acceleration or braking)

Its accurate if you have a constant speed over a few seconds or more.

[kiwi]

Speedometers and odometers will of course read differently simply by a variation of road wheel diameter, low profile tyres, worn tyres, odd makes, all can be different. Gibbo.

I can add gearbox set up and temperature variation to that mix. I got one oddball BX19TZS that defys all the common misconceptions of what a BX should be like and do.

[kiwi]

I tend to just drive the car at 3000ish odd revs when crusing, get good economy & because the speedo is showing 70, i'm fooled into thinking that i'm not going that slow, so can stick at that speed without any probs, been upto Newcastle & back & got 58mpg sticking to those revs.

If i'm driving on any other roads with other speeds, i just adjust my speed to be more than what the limit is, satnav say's 50 when speedo is showing 55, so i just remember the various one's, so as not to be a mobile chicane & oldman duffer driver

I found the 19TRS and TZS at 3100 RPM in 5th gear is 100kph (62mph) according to satnav. Even though the TRS shows 97 on the speedo and the TZS can be anything between 100 (on a cold day) to 106kph once the engine bay warms up.

Yea I got a weird BX