“…(2) Knowledge-based algorithms [27][28]: such algorithms can solve the limitations of statistical model-based algorithms, but it also introduces some more problems needed to be redefined in a new scene, including verification difficulties, large costs. (3) Model-based algorithms [29][30]: such algorithms first extract target features; then, construct spatial model of targets; next time, utilize selected features to initialize system parameters; finally, predict the location of targets via the characteristics of targets. (4) Neural networks-based and expert systems-based algorithms [31][32]: such algorithms can solve the problems which conventional algorithm cannot solve.…”