Using Digital Cameras on an Unmanned Aerial Vehicle to Derive Optimum Color Vegetation Indices for Leaf Nitrogen Concentration Monitoring in Winter Wheat. - Jiale Jiang; Weidi Cai; Hengbiao Zheng; Tao Cheng 003; Yongchao Tian; Yan Zhu 005; Reza Ehsani; Yongqiang Hu; Qingsong Niu; Lijuan Gui; Xia Yao (Remote. Sens., 2019)