Navigation device for an optical system for aiming and observing a scene, and method for determining an attitude for such an optical system

A navigation device configured to be securely mounted on an optical system for aiming and observing a scene, the navigation device being configured to determine a navigation attitude the navigation device comprising:

• at least one inertial module configured to determine a current inertial attitude continuously,
• at least one viewing module configured to capture at least one current image of the scene continuously, the inertial module and the viewing module being physically secured in their movements,
• at least one database storing a plurality of reference attitudes each of the reference attitudes being associated with a reference optical signature, and
• at least one computer configured to:
• compare the current inertial attitude with the reference attitudes so as to determine the closest reference attitude and deduce the associated reference optical signature,
• compare the current image captured by the viewing module with the associated reference optical signature so as to determine an angular offset, and
• determine the navigation attitude from the nearest reference attitude and the angular offset