1. Research Center of Information Technology, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China
2. College of Resources Environment and Tourism, Capital Normal University, Beijing 100048, China
3. Department of Plant Sciences, University of Tennessee, Knoxville, TN 37996, USA
4. Department of Environmental and Geosciences, Sam Houston State University, Huntsville, TX 77340, USA
5. College of Information and Electrical Engineering, China Agricultural University, Beijing 100083, China
6. School of Surveying and Land Information Engineering, Henan Polytechnic University, Jiaozuo 454000, China