Compact low-cost Arduino-based buoy for sea surface wave measurements

This paper presents and describes a compact low-cost buoy for measurements of sea surface wave properties. Small micro-electro-mechanical (MEM) acceleration-gyroscope-magnetometer sensor data are stored onto internal buoy memory using open source Arduino hardware. The buoy has extremely simple internal architecture and small size because of deliberate disregard of autonomy and endurance, which is not necessary in short-term oceanographic measurements. Raw sensor data are processed after the measurements, so that various approaches can be validated and applied. Procedures for determining the buoy hull orientation and recovering wave signals are proposed. Possibilities in estimation of wave spectra and directional and spatial-temporal wave properties are demonstrated. From static ground calibration and field measurements in sea we have found, that internal MEM noise is insignificant for typical wave measurements. Low and high frequency disturbances caused by wind induced tilting, wave breaking kicks and resonant motions of the hull are discussed. A good consistence of estimated wave spectra with visual data and empirical spectral level model is demonstrated. Encouraging coincidence of elevation spectra calculated from independent acceleration, tilt and rotation signals is found.