[pct-l] GPS, distance and speed.

[adrian.borner at ch.abb.com (adrian.borner@ch.abb.com)]

The accuracy of the GPS is in the range of 20 to 30ft horizontally and even
less vertically depending on reception. The misreading is not always in the
same direction and as a result the distance covered between two readings
could even be negative when walking. As a result from this random error the
accumulation i.e. distance covered and max speed are not accurate when you
move slowly.
Doing the same thing in a car cruising down a highway with 60mph, the
random error is much smaller in relation to the distance covered.
Adrian