Quote:
Originally Posted by TLAM Strike
Actually the Earth's magnetic field is constantly shifting and can be subject to local variances. GPS birds are on constant orbits, its the programmer of the GPS that is wrong.  |
It's also important to remember that GPS is reliable only if it has good signal to four or more satellites. With just three error propability is large. With one or two it's same as if those satellites does not exist at all.
In mountainous terrain good signal is far from guaranteed.