1. A mobile station comprising: an inertial sensor, wherein the inertial sensor provides inertia measurements; inertia measurement processor coupled to the inertial sensor to accept the inertia measurements and to determine an uncertainty based on the inertia measurements; and navigation position filter coupled to the inertia measurement processor to receive the uncertainty and to determine a position estimate based on the uncertainty, wherein the navigation position filter comprises a first position filter model to compute a first position estimate base on the uncertainty.