1. University of Electronic Science and Technology of China,School of Resources and Environment,Chengdu,China,611731
2. Xihua University,School of Computer and Software Engineering,Chengdu,China,610039
3. Ningbo University,Department of Geography and Spatial Information Techniques,Ningbo,China,315211
4. Ningbo University,Faculty of Electrical Engineering and Computer Science,Ningbo,China,315211
5. Communications and Information Technology Headquarters,Sichuan Provincial Public 7 Security Department,Chengdu,China,610041