1. A method of integrity monitoring for errors in a navigation system, the method comprising: receiving a plurality of signals transmitted from a plurality of space-based satellites; determining a full position solution for the navigation system based on the plurality of signals; determining one or more position sub-solutions for the navigation system based on the plurality of signals; setting a value for a pseudorange bias; computing a transformation matrix for the full solution and all sub-solutions using a Kalman filter; computing a bias effect on an error of a filtered state vector component for all sub-solutions; and adding the bias effect on the error of the filtered state vector component to computed protection levels for both vertical and horizontal dimensions.