[1] [1] Liu K, Zhang J T, Yan Z G. A method for improving landing error of UAV automatic return[J]. Modern Electronic Technique, 2018, 41(6): 61-64, 69.

[2] [2] Song Y, Weng X W, Guo X G. Small UAV localization method based on optical-flow and inertial navigation[J]. Transducer and Microsystem Technologies, 2015, 34(1): 13-16.

[3] [3] Zhao C H, Pan Q, Liang Y, et al. Video Imagery Moving Targets Analysis[Z]. Beijing: National Defense Industry Press, 2011.

[4] [4] Dji.A2－ User Manual of Flight Control System －V1.22－CN[Z]. Shenzhen: Innovation in DAJIANG, 2015.

[6] [6] Xiang X Z. Study of Circle Detection in Complex Condition[D]. Harbin: Harbin Engineering University, 2005.

[7] [7] Gonzalez R C, Woods R E. Digital Image Processing (Third Edition)[M]. Trans. by Ruan Q Q, Ruan Y Z, et al. Beijing: Electronic Industry Press, 2017: 404-406.