Sea Level Monitoring Using a Gnss-based Tide Gauge

A continuous monitoring of sea level changes is important for human society since more than 50% of the world’s population live within 60 km of the coast. Sea level is traditionally observed with tide gauges that give measurements relative to the Earth’s crust. To improve the understanding of sea level changes it is necessary to perform measurements with respect to the Earth’s center of gravity. This can be done with satellite techniques, and thus a GNSS-based tide gauge is proposed that makes use of both GNSS-signals that are directly received and that are reflected on the sea surface. A test installation at the Onsala Space Observatory shows that the reflected GNSS-signals have only about 3 dB less signal-to-noiseratio than the directly received GNSS-signals. A comparison of relative sea level observations from the GNSSbased tide gauge to traditional tide gauges gives an RMSagreement on the order of 4 cm.