Assessing Safety and Suitability of Old Trails for Hiking Using Ground and Drone Surveys. - Shiou Yih Lee; Chengju Du; Zhihui Chen; Hao Wu; Kailang Guan; Yirong Liu; Yongjie Cui; Wenyan Li 007; Qiang Fan; Wenbo Liao (ISPRS Int. J. Geo Inf., 2020)