1. Shaanxi Key Laboratory of 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, China
3. Faculty of Electrical and Computer Engineering, University of Iceland, Reykjavík, Iceland
4. Ministry of Education, Key Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions, Henan University, Kaifeng, China