Try this for an experiment:

Cover up your windshield and drive entirely by trying to follow the line
on you car's GPS system. That's what you doing on a boat in the fog.

Also, consider that the streets have been well mapped in the last few
years by survey companies that drive around in cars and mark each
intersection. Many nautical charts are based on century old data. Much
of the issue is the map/chart quality, not the accuracy of the GPS itself.

Actually, the boat gps is just as accurate, perhaps even better since
there is no shielding from high buildings. Its just that on a boat you
may be relying 100% on the GPS as the primary, and perhaps only, source
of position. In a car, you glance occasionally at the map plotter and
would never notice if the GPS sometimes said you were on someone's front
lawn.

One can easily imagine a situation on a boat where failure of the GPS
would cause you to drop anchor and wait until the weather clears; I
doubt you would do the same in a car!


BTW, my wife got a new car with a nav system just last night. It
currently in the driveway reporting two different street addresses
(depending on how you ask), both wrong. Both are actually nonexistent
addresses - one of them would be a hundred yards past the other end of a
dead end street. The actually position on the map is well reported,
however.


anchorlt wrote:
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?