1. Wuhan University, State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, No. 129 Luoyu Road, Wuhan 430079, China
2. Mississippi State University, Department of Electrical and Computer Engineering, Starkville, Mississippi 39762, United States
3. German Aerospace Center (DLR), Remote Sensing Technology Institute, Oberpfaffenhofen, 82234 Weßling, Germany