Calibration of sensors for indirect sea-wavemeasurement: Experimental aspects

The measurement of sea waves is a challenging task in dynamic measurement. There are many approaches to this kind of measurement and in all cases, calibration is a big challenge and a still open research topic, due to the difficulty, or even the impossibility, of developing a reference phenomenon. Therefore, calibration should in some way include modelling steps, as it is often the case in dynamic measurement. In this study, the measurement of the sea wave motion by an Inertial Measurement Unit (IMU) is considered and the calibration of the IMU is investigated, both including its embedded software or acting directly on the raw acquired time series. To this purpose a dry calibration device operated under a reference external instrument is introduced and some results for two sensors are discussed, one with internal processing firmware to obtain wave period and height (or heave), the other associated with a custom algorithm. Indoor and outdoor tests are compared, to investigate the possibility to use the proposed wave simulator as a transfer standard for wave height.