Abstract: A complete track initiation frame is provided based on an analysis of the traditional track initiation algorithms and the existent group target track initiation algorithms with the aim of solving the refined track initiation problem of targets in a group, and a refined gray track initiation algorithm of group targets based on relative position vectors is proposed. Firstly,a preparative division and association of the group targets are performed based respectively on the circular threshold model and the group center. Secondly, the corresponding coordinates of the preparative associated groups are found, and then the relative position vectors of the measurements are built, The measurements in the groups are associated with the refined gray association model. Finally, the group target state matrix is obtained with the track validation rule. An analysis of the results of the simulation data shows that the overall performance of this algorithm is better in terms of true track initiation, false track restraint and adaptation to clutters as compared with the modified logic algorithm and the multi-formation track initiation algorithm based on clustering and Hough transform,

Key words: group target, relative position vector, refined gray association model, corresponding coordinates, track initiation