  We report on the retrieval of directional sea surface roughness, in terms of
its full directional mean square slope (including direction and isotropy), from
Global Navigation Satellite System Reflections (GNSS-R) Delay-Doppler-Map (DDM)
data collected during an experimental flight at 1 km altitude. This study
emphasizes the utilization of the entire DDM to more precisely infer ocean
roughness directional parameters. In particular, we argue that the DDM exhibits
the impact of both roughness and scatterer velocity. Obtained estimates are
analyzed and compared to co-located Jason-1 measurements, ECMWF numerical
weather model outputs and optical data.
