1. School of Earth Sciences and Resources, Chang’an University, Xi’an, China
2. Department of Mathematics and Information Science, College of Science, Chang’an University, Xi’an, China
3. State Key Laboratory of Resources and Environmental Information Systems, Institute of Geographic Sciences & Natural Resources Research, Chinese Academy of Sciences, Beijing, China
4. University of Chinese Academy of Sciences, Beijing, China
5. School of Land Engineering, Chang’an University, Xi’an, China