Sea surface oil slick detection from GNSS-R Delay-Doppler Maps using the spatial integration approach

This paper investigates the methodology of applying the spatial integration approach (SIA) to the scattering coefficient retrieval from GNSS-R signals for sea surface oil slick detection. The SIA has been traditionally used in the generation of simulated Delay-Doppler Maps, which emphasizes the power contribution of every sea surface point. While in this paper, the SIA is applied to the scattering coefficient retrieval with a reasonable approximation to relate the Delay-Doppler domain and the spatial domain. To validate this approach, a simulated Delay-Doppler Map over an oil slicked area based on the measured oil data and wind speed of an actual oil spill event is analyzed. Particularly, the configuration of the UK-DMC GNSS-R receiver, which includes its sampling rate and noise level, is considered in the oil slick detection process. A theoretical comparison between the commonly used Jacobian approach and the SIA reveals their differences in methodology and the cause of errors. The result indicates that with acceptable extra time consumption, the SIA increases the accuracy of the scattering coefficient retrieval algorithm, especially in the area surrounding the ambiguity-free line.