Evaluation of a GNSS Buoy With Real-Time Precise Point Positioning Ability for Monitoring Tides and Ocean Waves

Considerable demand exists for precise sea surface height data to assess tide level, ocean wave height, tsunami height, and sea level in offshore regions. However, the limited availability of structures for installing water level sensors necessitates the adoption of innovative observation technologies in these areas. This study developed a global navigation satellite system (GNSS) buoy with real-time precise point positioning (RT-PPP) capability to monitor sea levels in nearshore and offshore areas. The TerraStar-C PRO service (Novatel Inc., Calgary, AB, Canada) was employed for RT-PPP. A static laboratory test indicated that the standard deviation for all measured height data was 0.016 m. Moreover, in a kinematic laboratory test, the wave height error was −0.2%. Thus, the RT-PPP performance was satisfactory. A field test indicated that the tide data measured by the developed GNSS buoy closely matched those recorded at a nearby tide station, with the root mean square error between the two sets of data being 0.074 m. Additionally, the significant wave heights obtained from GNSS were refined using a linear regression method. The significant wave heights, mean wave periods, peak wave periods, and dominant wave directions obtained from the GNSS sensor were generally consistent with those acquired from an accelerometer–tilt–compass wave sensor, with the root mean square errors in these parameters being 0.11 m, 0.13 s, 0.63 s, and 10.0°, respectively. In summary, the results of this study indicate that the developed GNSS buoy with RT-PPP ability is a viable tool for monitoring tides and ocean waves in nearshore and offshore areas where real-time kinematic ambiguity resolution is unreliable.