1. Shaanxi Key Laboratory for Network Computing and Security Technology, School of Computer Science and Engineering, Xi’an University of Technology, Xi’an, China
2. Department of Geography and Spatial Information Techniques, Ningbo University, Ningbo, Zhejiang, China
3. Faculty of Electrical and Computer Engineering, University of Iceland, Reykjavik, Iceland
4. State Key Laboratory of Rail Transit Engineering Informatization (FSDI), Xi’an, China