This paper addresses a conceptual study on a precise passive target localization approach for substation facilities inspection using unmanned aerial vehicle (UAV) under GPS-denied environments. First, a cruciform receiver array that provides the range difference (RD) measurements between a facility (receiver array) and a UAV (transmitter) is devised. Then, to effectively deal with the real-time and accurate localization performance issue, our RD-based target localization problem is reformulated from the viewpoint of the linear least-squares estimation theory, and constrained robust weighted least-squares (C-RWLS) estimation scheme is applied. The proposed method shows excellent location estimates with the help of hard constraints on the geometric relation to the transceivers. Also, it is suitable for real-time implementation due to its linear structure. The reliability of the proposed estimation method is demonstrated through simulations from various points of the UAV.
