how accurate are

[scottbott]

satnavs for the speed they read,I have 215/55/§6 tyres and the speedo reads 60mph and the satnav say's 58 mph,I reckon that is pretty good as I will always be a bit under the speed showing on the speedo and not have to worry too much about speed cameras as long as I use the speedo as a reference

[AdrianC]

The satnav is more accurate than your speedo.

But no speed camera will nick you for 61 in a 60, anyway. 10%+2mph is the guideline they won't usually prosecute below.

[voodoopenguin]

The satnav is more accurate than your speedo.

But no speed camera will nick you for 61 in a 60, anyway. 10%+2mph is the guideline they won't usually prosecute below.

Agree that the satnav is the most accurate.

On that second point you sometimes hear people complaining that they were done for doing 42 in a 40 zone, "Haven't the cops got better things to do other than nicking me for doing 2mph more than I should?" What they were probably doing was more like 46 and then the police took off that 10% and 2mph.

Paul

[MattBW]

The satnav is more accurate than your speedo.

But no speed camera will nick you for 61 in a 60, anyway. 10%+2mph is the guideline they won't usually prosecute below.

Unless its cambridge or parts of Wales

[LeeME3]

Satnav is very accurate when cruising, but not particularly so when accelerating / decelerating though (due to acquisition lag, signal latency and the fact that most still use the older P codes). However, we are talking T25s here so acceleration is not a major issue!

[bigherb]

Satnav is very accurate when cruising, but not particularly so when accelerating / decelerating though (due to acquisition lag, signal latency and the fact that most still use the older P codes). However, we are talking T25s here so acceleration is not a major issue!

Yep nor when going up and down hills, Satnavs measure the linear speed across the ground it'll read slower when going up and down hills about 4 mph when going up the hill out of my valley.