HydroSwarm: towards fine resolution 2D imaging of surface water with GNSS-R flight formation

It is recognised that GNSS reflectometry (GNSS-R) is uniquely suited to measuring flooding under clouds and under forest canopies because of the L-band and forward scatter nature of the measurements. GNSS-R picks out coherent reflections from flat surfaces at higher resolution than incoherent reflections from elsewhere. When a surface is sufficiently flat, such as inland water or flooded areas, the coherent reflections offer a resolution of sometimes better than 1 km. The drawback is that as the resolution increases, the track footprint becomes thinner, and only a cross-section of information about the surface is produced from each track. If a 2D map is required, the picture must be built up by multiple passes from multiple satellites.