Doppler Aided Inertial Navigation (DAIN) facilitates the determination of position, velocity and direction of mobile devices operating in highly obstructed GPS/GNSS environments. Delivering high precision, high resolution positioning information using signals of opportunity, the present invention measures the Doppler shift of a moving device using a variety of signals combined with inertial accelerometers and environmental sensors to deliver an autonomous positioning and navigation capability that does not require external infrastructure or a priori knowledge of signal sources.