On Tue 06 Oct '09 at 21:03 lal_truckee wrote:

Humsquirto wrote:

72mph! I'm pretty sure the GPS speed indicator is accurate, ...

I profess a slight doubt...


This generated a lot of discussion amongst people I know too, here's
some facts:

http://www8.garmin.com/products/etrexVistacx/spec.html

GPS accuracy:
Position: 15 meters, 95% typical*
Velocity: 0.05 meter/sec steady state

i.e. 0.05 (meters per second) = 0.111846815 mph

Remember that the position error is constant between the velocity
measurements, thus cancels out.

Though this assumes a good signal the entire time, and you should
check the individual track log points.

I've seen 600mph+ readings sometimes with bad GPS signal and massive
non constant positional errors.




A.

--
Alun Evans