Na Qiao^1,2, Lixin Wang², Lifu Zhang¹, Changping Huang¹, Gillian Maggs-Kölling³ and Eugene Marais⁴, (1)RADI Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing, China, (2)Indiana University Purdue University Indianapolis, Department of Earth Sciences, Indianapolis, IN, United States, (3)Gobabeb Research and Training Centre, Walvis bay, Namibia, (4)Gobabeb Research and Training Centre, Walvis Bay, Namibia