Sea-Level Analysis Using 100 Days of Reflected GNSS Signals

Global Navigation Satellite System (GNSS) signals reflected off the sea surface can be used for remote sensing of the sea level. We present results from a GNSS-based tide gauge using standard geodetic-type GNSS receivers for receiving both the reflected and the direct GNSS signals. The local sea level is then obtained using relative geodetic processing of the carrier phase delay.We show results from our analysis of 100 days of GNSS data from the Onsala Space Observatory (OSO). The GNSS-derived sea level is compared to a weighted average of sea level observations from two stilling well gauges located 18 km and 33 km away from OSO. The comparison shows a high level of agreement with a correlation coefficient of 0.96. Furthermore, the standard deviation (1σ) between the time series is 5.0 cm and the pairwise mean difference is 3.6 cm.Additionally, we present a tidal analysis of the three sea level datasets and compare the derived tidal constituents both to each other and to a Regional Tide Model (RTM). From the GNSS-derived sea level we find significant ocean tidal signals with reasonable amplitudes and with most phases in between those for the stilling well gauges sites. The comparison to the RTM shows limitations of the model for long-period tidal signals