“…In recent years, three main strategies have been used to achieve drone swarms’ persistent surveillance [ 8 , 11 , 12 , 13 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]: (i) on-duty UAV replacement scheme based on recharging stations [ 13 , 19 , 25 ]; (ii) energy-efficiency path planning [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]; and (iii) novel structures of UAV teaming [ 8 , 11 , 18 , 22 ]. UAV distribution’s hierarchical architecture helps plan efficient and adaptive surveillance missions when the surveillance map changes due to weather or invisible factors.…”