Examining the Performance of the Sentinel-3 Coastal Altimetry in the Baltic Sea Using a Regional High-Resolution Geoid Model

Performance of the Sentinel-3 SRAL altimeter is evaluated in the coastal zones of the Gulf of Finland, Baltic Sea. Sea Surface Heights (SSH, processed with the ESA developed SAMOSA 2 retracker) were computed at six passes for 2017 nearby three tide gauge (TG) sites in Estonia. These SSH were compared with the TG records in conjunction with an operational hydrodynamic model (HDM), both referring to a high-resolution national geoid. The Sentinel-3 data quality assessment yielded the root mean square error of 70 mm with respect to the TG+HDM derived SSH. The near-zero mean of discrepancies shows that there is no significant systematic bias between the land-bound geodetic infrastructure and Sentinel-3 SSH data. This accuracy is within the range aimed for modern marine geoid modelling (i.e. 5 cm).