Wave measurements with a modified HydroBall® buoy using different GNSS processing strategies

One of the CIDCO’s (The Interdisciplinary Center for the Development of Ocean Mapping) HydroBall® GNSS buoys has been specifically adapted to evaluate its potential for wave measurement at centimeter accuracy level. Multiple GNSS processing strategies were tested, namely PPK (Post-Processed Kinematic), PPP (Precise Point Positioning), and TRP (Time Relative Positioning). Experiments were carried out in a hydraulic flume where waves of different amplitudes and periods were generated in a controlled environment. The wave heights obtained by the various GNSS solutions were compared with ultrasonic gauge measurements placed along the flume. The best results were obtained with the PPK and TRP solutions with root mean squared (RMS) values of 2 cm (on average). The main advantages of the TRP solution are that it does not require any reference station nearby (contrary to PPK) or precise ephemerides (required by PPP). A sinusoidal regression comparison of the wave height time series allowed determination of the wave period and amplitude with mean errors of 0.06 s and 0.8 cm, respectively.