This paper presents a novel method for fusing data from a UAV's range and vision sensors. The range sensor is used to build an elevation map of the flying area. Fuzzy logic is used to detect red barrels in camera images. The world location of a target on the ground is found by fusing the terrain map with image data using both an extended Kalman filter and a particle filter. The target detection system has been tested using images collected onboard a UAV. The terrain mapping system and the fusion system were both tested in simulation.