Wave Coherence in GNSS Reflectometry: A Signal Processing Point of View

The enduring activity of CYGNSS and TDS-1 observatories has provided clear evidence that ground reflected GNSS signal can be exploited for mapping of geophysical quantities in climate and global monitoring applications. One main challenge is to find out useful variables for determining the level of coherence of the scattered wave in the presence of complex natural landscapes such as water basins, river floods, mixed ice and water. In this study, we approach the concept of wave coherence by analyzing the persistence of signal energy across principal directions, determined via generalized eigenvalue decomposition of the DDM delay waveform correlation matrix. An example shows that the dimensional spread of the eigenvalues is finely sensitive to coherence of the ground reflected wave.