Well, there are two ways, one is to tape the GPS to the tank, the other is to use the mile markers on the freeways, just time yourself over a distance, in 6 minutes you should see 10 go by at 100km/h
Theres no such thing as satellite lag, the GPS works by making a number of extremely precise calculations which are quite power intensive, so most devices which aren't linked to a vehicles power systems (like dataloggers) will only do the calculation a few times a second, if that. Mobile phones, not being dedicated GPS devices will update a lot less freqently than that even, sometimes waiting over a second between updates. Thats what you're seeing when your phone doesn't update frequently, not "satellite lag".aj26 said:GPS does have satellite lag and due to weather conditions as well it can affect what "determined speed" you are getting. When I'm driving my GPS will say I'm doing 75 when my speedo says 80-82.
My mobile GPS that I use is very very slow and will say I'm doing 0 when I'm already doing about 30, or even saying that my mobile will say I'm doing 10km lower than the actual.
Normally when I'm going past a speed camera I will look down and drop my speed at 10km (60 zone I'll do 50), Just incase if the thing decides to book me I can say no I was doing 50 at the time.
What can speed checkpoints do? Because I remember when heading down to Wagga Wagga there was a couple and people were doing 130-150 in a 110 zones.
The dyno isn't going to be awesomely accurate because the tyre is compressed onto the roller, giving you a different rolling radius and also the tyre will tend to give you a different slip on the roller because of the whacky contact patch.muzza said:or you could chuck it on a dyno?
that would definately be the easiest if your speed is measured in the gearbox/back wheel.