1.Changjiang Spatial Information Technology Engineering Company, Wuhan 430010, China
2.Department of Computer, Wuhan Ordnance N.C.O. Academy of PLA, Wuhan 430075, China
3.School of Geography & Environmental Management, University of Waterloo, Waterloo, ON N2L2R7, Canada
4.School of Remote Sensing Information Engineering, Wuhan University, Wuhan 430079, China