1. School of Computer Science and Engineering; Shaanxi Key Laboratory of Network Computing and Security Technology, Xi’an University of Technology, Xi’an, Shaanxi, China
2. Department of Geography and Spatial Information Techniques, Ningbo University, Ningbo, Zhejiang, China
3. School of Electronic Information and Artificial Intelligence, Shaanxi University of Science and Technology, Xi’an, China
4. Faculty of Electrical and Computer Engineering, University of Iceland, Reykjavik, Iceland
5. School of Engineering and Information Technology, University of New South Wales, Canberra, ACT, Australia