A Triangle Algorithm of Stars Identification Improved by Geometric Hull

Triangle algorithm and its modified techniques are used widely in the field of star pattern recognition. However, efficiency and reliability remain key issues. A novel improved triangle algorithm restrained by geometric hull of stars in the field of view, is presented. First, the set of navigation stars in one field of view (FOV) is obtained by three methods. Second, the convex hull is found for the set of stars, then, all possible triangles obtained by any three connected Vertexes of hull, is stored as two connected line segments and their vertex angle moving clockwise from the shortest segment. A speedy match method was formulated; these vertex angles are used in a tiered logical algorithm to establish the triangle-ID, making the vertex angle as a function of triangle -ID by Curve Fitting. Finally, the probability is used to solve the redundancies of the observed stars and the mapped navigation stars. Simulation is carried out，the number of navigation star triangles is reduced to rational level by the restriction of geometric hull, shows that the algorithm proposed in this paper has the advantage in terms of robustness against the star position noise. Also, the identification rate and the storage requirement are improved by the algorithm, as compared with the conventional triangle algorithms.