Star Identification Based on Hash Map

A fast and robust star identification algorithm based on hash map is proposed in this paper. The algorithm is derived from the classical triangle feature matching algorithm but significantly improves the efficiency and robustness. By mapping each triangle feature to an integer and building a hash map of all the triangle features, the proposed algorithm is capable of matching a triangle feature with the computational complexity only O(8); based on this characteristics, a double-triangle verification method is proposed to improve the robustness of identification; moreover, an optimized strategy for triangle feature selection is proposed, which further improves efficiency of the algorithm. Experimental results on both simulation images and night sky images show that the proposed algorithm is quite robust to false stars, position noise and magnitude noise. The identification rate of the algorithm is higher than the grid algorithm and similar to the pyramid algorithm, while the identification speed is up to 100 times faster than the pyramid algorithm.