Precise Ground-Based GNSS-Reflectometry Sea Level Measurements Using Low-Cost Antennas

GNSS-Reflectometry (GNSS-R) tide gauges are a promising alternative to traditional tide gauges due to easier and cheaper maintenance in remote environments. GNSS stations that have been used for reflectometry purposes thus far are designed for monitoring land motion and may cost more than 10,000 each. We have found that a low-cost GNSS antenna (< 100) can be used to make equally precise sea level measurements, with an RMSE of a few centimeters when compared to a collocated tide gauge. However, an RMSE of less than one centimeter is desired for sea level research purposes. We have developed a modelling technique to estimate the precision and sources of error in GNSS-R sea level measurements by creating and analyzing a time series of synthetic Signal-to-Noise-Ratio (SNR) data. Our modelling work demonstrates that two of the dominant sources of error are the effects of random noise in the SNR data and atmospheric refraction. In light of this, we have designed a new technique to precisely monitor sea level by using multiple low-cost GNSS antennas in the same location. Initial results from modelling and observations indicate that multiple antennas can be used to reduce the effect of noise and to improve corrections for the effect of atmospheric refraction. This new approach provides more precise sea level measurements at a lower cost than stations that have been used in previous GNSS-R literature.