anchorlt wrote in message
om...
I keep reading about GPS for boats and how innacurate it can be.

Why is the same not innacurate in cars?

My car GPS is so accurate it tells me I am on the white line at a
traffic signal stop light or in my driveway.

Why not the same for boats?

I have been told that factory GPS and most high-end retrofit systems for
cars also use a speed sensor input from the car transmission that is
separate from the GPS signal. It is used primarily to keep position
calculations going when the satellite signal is lost (tunnel) but it also
helps improve the accuracy of the position readings.

Eisboch