The present disclosure relates generally to optical flow algorithms. Section 1 of the present disclosure describes an optical flow algorithm with real-time performance and adequate accuracy for embedded vision applications. This optical flow algorithm is based on a ridge estimator. Sections 2 and 3 describe an obstacle detection algorithm that utilizes the motion field that is output from the optical flow algorithm. Section 2 is focused on unmanned ground vehicles, whereas section 3 is focused on unmanned aerial vehicles.