Attitude determination and alignment using electro-optical sensors and global navigation satellites

A method for determining refined attitude information for a vehicle, comprising:

• receiving radio-frequency signals from a plurality of GPS/GNSS navigation satellites and applying a Kalman filter to determine expected position and motion of the vehicle from the received radio signals;
• determining coarse attitude information for the vehicle;
• selecting one or more satellites for refining the coarse attitude information of the vehicle;
• determining expected angular position and motion of the selected one or more satellites relative to said vehicle, equipped by way of a GPS/GNSS antenna/receiver unit and an inertial navigation system;
• measuring actual angular position and motion of the selected one or more satellites about two axes relative to the vehicle using an onboard electro-optical sensor and an inertial measurement unit;
• computing a difference, along two axes, between the expected angular position and motion and the measured angular position and motion of the selected one or more satellites;
• and
• refining the coarse attitude information from the computed difference.