1. School of Geography and Tourism, Shaanxi Normal University, Xi’an 710119, China
2. School of Geographical Sciences, Shanxi Normal University, Taiyuan 030031, China
3. State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Beijing 100101, China
4. Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing 210023, China