difficult for a human operator to observe and command. Some missions will require rapid decision making based on more targets than a human can process. Finally, missions may utilise swarms of UAV systems for which the workload would be too immense for a human to control.Vision-based feedback can be a critical component to autonomy. Inertial sensors, such as gyros and accelerometers, provide information about the state of the vehicle; however, they do not provide any information about the environment. Vision can be used to extract information, such as location of obstacles, about the flight space. As such, vision-based feedback provides a mechanism for autonomous navigation to maneuver through unknown or uncertain environments. Even urban environments can be considered given that appropriately sized vehicles, having wingspan less than 2ft and turn radius less than 20ft, can respond quickly to information obtained from cameras which often have field of view between 70 degrees and 140 degrees.The concept of visual-servo, or vision-based, control is appropriate for tasks such as guidance and navigation. Researchers in robotics have been particularly active in this area along with more recent applications in aerospace and manufacturing. Most techniques share some commonality; namely, a sequence of image processing and vision processing are performed to extract information which is then analysed to make an optimal control decision. The basic unit of information from an image is a feature point which indicates some pixel of particular interest due to, for example, colour or intensity gradient near that pixel. Among the techniques that utilise feature ABSTRACT Vision-based control is being aggressively pursued for autonomous systems. Such control is particularly valuable for path planning to achieve mission objectives like target tracking and obstacle avoidance. This paper presents a multi-rate strategy that utilises a fast-rate optic flow approach and a slow-rate scene reconstruction approach. The vehicle uses scene reconstruction to generate an accurate map for path planning; however, optic flow is used to avoid obstacles while the scene reconstruction is computed. A switch element is used in the feedback path to determine whether information relating to the reconstructed map or the optical flow should be used for navigation. The resulting controller is able to generate flight trajectories and perform obstacle avoidance within a computational cost which is reasonable given performance demands and computational resources on a wide range of aircraft. A simulation demonstrates the performance of an aircraft that uses the multi-rate controller to avoid an obstacle which is only observed after a turn. Essentially, the fast-rate optic flow indicates the presence of the obstacle during the time that slow-rate scene reconstruction is being performed. The resulting flight path is able to follow mission objectives and avoid a collision.