GPS Signal Land Reflection Coherence Dependence on Water Extent and Surface Topography using Cygnss Measurements

Precise carrier phase measurements from coherent reflections of Global Navigation Satellite Systems (GNSS) signals are poised to enable new capabilities in Earth remote sensing. However, there is still much to learn about the reflection conditions that produce coherence. For land reflections especially, the degree to which various surface characteristics impact coherence is unclear. In this paper, we explore the dependence of coherence on four surface characteristics: maximum water extent, surface topography, soil moisture, and vegetation water content. To quantify the level of coherence, the phase is tracked from two sets of CYGNSS raw IF data and the circular length of the changes in phase is calculated. A strong link is found between coherence and the presence of surface water; the impact of the other surface characteristics on coherence is still under examination.