1. School of Geography and Information Engineering, China University of Geosciences (Wuhan) , Wuhan 430074, China
2. State Key Laboratory of Geo-Information Engineering, Xi'an Research Institute of Surveying and Mapping , Xi'an 710054, China
3. School of Environment Science and Spatial Informatics, China University of Mining and Technology , Xuzhou 221116, China
4. Department of Geoscience and Remote Sensing, Delft University of Technology , CN Delft 2628, The Netherlands