1. Department of Signal Theory and Communications, Universitat Politècnica de Catalunya (UPC) and IEEC-UPC, Barcelona, CommSensLab--UPC, Spain
2. Image Processing Laboratory, Universitat de València (UV), València, Spain
3. Microwave and Radar Institute, German Aerospace Center (DLR), Weßling, Germany
4. Institute of Marine Sciences, Spanish National Research Council (ICM-CSIC), Barcelona, Spain
5. Department of Biosystems and Agricultural Engineering and the Department of Civil and Environmental Engineering, Michigan State University, East Lansing, MI, USA
6. Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA