GNSS Interferometric Reflectometry as an Operational Framework for Real-Time Tide Estimation

This study focuses on the advancements in global navigation satellite system interferometric reflectometry (GNSS-IR) for operational and near-real-time tide estimation at Quarters Point in Washington, United States. By applying a predicted tide through integrating tidal constituents into the GNSS-IR framework, this research overcomes limitations of traditional GNSS-IR tide monitoring that suffer from low temporal resolution and simplicity. The method utilizes signal-to-noise ratio (SNR) data from satellite signals, which are affected by multipath interference as they reflect off water surfaces. The interference pattern of the multipath signal provides precise data on water surface heights, critical for accurate tide measurement. The key innovation in our approach is the near-real-time application of GNSS-IR, which is realized by incorporating a stochastic constraint using tidal constituents as prior information to enhance the accuracy of water level predictions. Preliminary results and validation efforts show promising outcomes. The GNSS-IR water levels were cross-validated against in situ measurements at Quarters Point, revealing a mean error of 5.2 cm with a standard deviation of 10.31 cm over a tidal range of approximately 5 m. This validation not only assures the reliability and consistency of the method but also highlights its robust capability in monitoring significant sea level changes. Our findings demonstrate that GNSS-IR, enhanced with tidal constituents and near-real-time processing capabilities, significantly improves the precision and responsiveness of water level monitoring systems. This advancement not only increases the effectiveness of coastal management strategies but also enhances disaster preparedness and ecological conservation efforts. The successful deployment and operation of this technology at Quarters Point indicates its potential for an additional tool for water level monitoring within the Northwest Association of Networked Ocean Observing Systems (NANOOS) water level network.