We present a novel single-camera 3-D spatial localization method using optical triangulation with temporaldifference image processing. The proposed system uses a blinking LED circle attached to the target as a marker. The background image except the marker circle is removed by applying temporal difference of the images since the imager samples at twice of the target blinking frequency. The 3-D spatial location can be calculated using simple equations to save computing energy without computing triangulation functions. The proposed method can be applied in low-power outdoor unmanned aerial vehicle (UAV) localization applications. The experimental results show that the proposed method can measure an object with an error of 0.4 m in the range of 30 m, or 0.1 m in the range of 3 m. The proposed method provides an attractive low power solution for remote UAV alignment and control.