To improve localization precision of small UAV

a localization method based on a kind of optical-flow system and its integration to an inertial navigation system is presented. After introduction of working mechanism of optical-flow sensor

establishment of mathematical models of optical-flow and analysis on measurement error of optical-flow

a dual optical-flow sensor is adopted to measure height and velocity of UAV

and real-time position

velocity and attitude can be obtained by using an extended Kalman filter（ EKF） to fuse the two-dimensional optical-flow information with strap-down inertial navigation system（ SINS）. The experimental results in indoor environment indicates that the proposed method can effectively improve localization precision and reduce error of navigation parameters such as position

velocity and attitude.