A mobile station database of cellular identifications and associated
position information is stored in mobile station memory. The mobile
station uses the position information in the database to assist in
determining a current position for the mobile based on an identifier,
such as cell ID, base station BSIC, PSC, or carrier frequency. A
satellite vehicle signal is searched in an uncertainty region that is a
function of position information associated with the current identifier.
The uncertainty region can be limited by assumed platform dynamics via
predefined velocity and acceleration information. Time maintenance for
the mobile station can also be achieved through known approximate
position from the position database and measurement of a single satellite
vehicle propagation delay. The mobile station can compare a position
determination obtained through satellite vehicle signals with position
database information to determine the validity of that position.
Out-of-network position information is also stored in the position
database and is optionally shared with a network.