Sat nav or speedo

Hi all,
does anyone know which is most accurate, the sat nav or the speedo.I only ask because when coming back from Headcorn yesterday i noticed that my speedo was saying 80mph but the sat was only saying 72.Which one is right?

SAT NAV every time

your speedo is designed to under read your actual speed, it only has to be with in either 7 or 10%, i cant remember. this is to allow you to never be speeding because of your vehicle. in other words, LR would rather it underread than over read, think of the legal crap if you were clocked at 78mph when your speedo was saying 70.

bla bla you get the drift.

coming from an IT background, i would swear your GPS is correct, i use my road angle insted of my speedo.
just remember, if it looses signal, from trees/urban forrests then it will miss read. also it is only an average speed over usually one second. so if your acellerating then if will display a speed slower than you are traveling, and if you are breaking it will show a speed faster than you are traveling.

also, the faster you travel, the more acurate it is.
basicly trust in on duel carrageways, and motorways, but keep to your speedo around town, afterall, those few MPH your missing in 30's could save a kid.

hey, loadofmeat, you sort your clutch out?

Sort of, its better than it was but not spot on.Thinking that i might phone Tim at Treedown on Monday and run it by him as he has worked on the truck before.

fair play.
i didnt think of it yesterday, but there is a fecking sh1t hot place in cullomption that does 4x4's.

Blackdown 4x4 Centre, Devon - Servicing & Repairs for all four wheel drives, Land Rover Sales, Land Rover Servicing, Land Rover Repair

they are very well known around your area.

Thanks for that it sounds just the place im looking for.

GPS is more accurate that your regular speedo. All speedos are a bit out (normally read faster than you are going) unless the are calibrated. Car do not (normally) have calibrated speedos although you can get them done. Police traffic cars (not pandas or vans!) and heavy commercial vehicles (those with tachographs) are all calibrated.

In my car 60mph on the speedo is 55-56mph on GPS. Using the same GPS when I am driving a coach and 60mph on the speedo is 59-60mph on GPS.

Cheers

Rog