Techniques are disclosed for systems and methods to provide relatively accurate position data from a plurality of separate position sensors. A system includes a logic device configured to communicate with a position sensor coupled to a mobile structure. The logic device is configured to receive positions of the position sensor and/or velocities corresponding to motion of the position sensor from the position sensor and determine an estimated relative position of the mobile structure based, at least in part, on the received Doppler-derived velocity and a prior estimated relative position of the mobile structure.