Heh - this GPS lark is pretty funny :)
The TI's digital speedo seems fairly accurate - GPS rekoned 117mph at an indicated 120mph. Couldn't test it any quicker cos I ran out of road.
The 3-4mph seemed rather consistent though - 66mph at an indicated 70mph etc.
Tim, I think your Volvo must be broken :)
As I've not had it out on track, 60 GPS = 66 speedo. It's about 10% over throughout.
mines only 4mph different from the speedo
60mph = 56mph gpsRonny
You back from holiday then? Have a good time?
Peter
'bout the same as my Mondeo..
Yeah - mine was pretty much 3-4mph different at all speeds.
GPS speed is a minimum, rather than accurate.
At constant speed and on level, straight, roads, though the GPS figure will usually be pretty much spot on.
It is quite normal for a car speedo to read higher than the actual speed, this is to take account of different tyre sizes / pressures and is a legal thing to meet type approval.
With the "secret menu" on my car, I can see what the computer actually thinks my speed is, 3mph less than it tells me via the speedometer. Testing this is not necessary as GPS agrees with the computer speed, not the speedo. The other technique is to time how long it takes to do one mile on the odometer / road marker posts at an indicated 60 mph.
I've only found one car that read the same as GPS, a little Corsa was in the same mph.
Don't believe the speed figure when accelerating, it will lag behind quite significantly, similarly it will be wrong when decelerating, and can be misleading if going up or down hill, because the altitude is the least precise value and change in altitude increases the error in the lateral figures by some margin, leading to some confusion to any raw figures. If a corner is sharp, that will also give some inaccuracy.
Shit, HTH.
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