This paper proposes a novel method for positioning using Low Earth Orbit (LEO) signals of opportunity. A stationary base-station and roving receiver framework is presented wherein the base-station performs Angle of Arrival (AOA) estimation of the LEO signals to obtain azimuth and elevation angles and shares them with a roving receiver. With the AOA estimates and differential Doppler positioning, there is no need for either the base station or roving receiver to have precise knowledge of the LEO satellite states. In this way, a constellation agnostic positioning approach that addresses one of the primary issues with navigation from signals of opportunity - the lack of knowledge of transmitter states - is developed. The accuracy requirements of the AOA estimates are investigated and the feasibility of this positioning method is discussed. The results of this analysis will show that with a single constellation, the range of noise on the AOA estimates that will produce acceptable position estimates is severely limited. As multiple constellations are used and the number of measurements increases, it becomes more resilient to distortion in the geometry matrix and noise on the Doppler measurements.
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