The Preliminary Discussion of the Potential of GNSS-IR Technology for Terrain Retrievals

The expansion of research and applications of Global Navigation Satellite Systems (GNSS) has revealed the information of reflecting surface in inherent multipath errors. GNSS signals, usually used to measure position, have been demonstrated that they can be used to retrieve water properties including water level, soil moisture, snow depth, and vegetation water content, which are important for climate analysis and water resources monitoring. Reflected GNSS signals with different azimuths can carry information of the corresponding reflecting zone, which means every reflected signal has distinct “signal-to-noise ratio (SNR) characteristics” influenced by specific reflecting zones—and the parameter named “Reflector Height (RH)” deduced from SNR frequency is focused on in this study. Thus, after interpolation of a series of reflector height by coordinates of the footprint, products describing highly detailed terrain over a reflecting footprint can be produced. Data of three GNSS sites in EarthScope Plate Boundary Observatory, named P025, P351 and P101, was used to evaluate the terrain after calculating the terrain slopes and correcting the footprint following the slopes. A comparison of the results with a digital elevation model (DEM) showed that it is possible to retrieve terrain by GNSS-Interferometric Reflectometry (GNSS-IR); and the comparison with terrain slopes from DEMs in previous research also validated its potential.