This thesis describes the research of an obstacle detection system for a low flying autonomous unmanned aerial vehicle (UAV). The system utilized an extended Kalman filter based simultaneous localization and mapping algorithm which fuses navigation measurements with monocular image sequence to estimate the poses of the UAV and and NSERC (Collaborative Research and Development Grant and Discovery Grant) for their financial support. At last but not the least, I would like to thank my husband Hao Liu, my parents, and my parents in law for their support over the years of my studies. iv