1. Key Laboratory of Geographic Information Science (Ministry of Education), East China Normal University, Shanghai, 200241, P. R. China
2. Department of Computer Science, Wuhan University of Technology, Wuhan 430063, P. R. China
3. Provincial Key Laboratory for Computer Information Processing Technology, Soochow University, Suzhou, P. R. China
4. Beijing Key Laboratory of Big Data Technology for Food Safety, Beijing Technology and Business University, P. R. China