[1] Xian Univ Sci & Technol, Coll Geol & Environm, Xian 710054, Peoples R China
[2] Henan Polytech Univ, Coll Geomat & Land Informat Engn, Jiaozuo 454000, Peoples R China
[3] Xian Univ Sci & Technol, Coll Geomat, Xian 710054, Peoples R China
[4] Chinese Acad Sci, Inst Soil & Water Conservat, Minist Water Resources, Yangling 712100, Peoples R China