Wireless sensor network for the accurate measurement of yacht freeboards

Measuring the freeboard height is fundamental for boat builders and hull designers, because it provides precise information about the ship's displacement as well as its trim when floating, but no electronic system to carry it out is available. We describe here a wireless sensor network, consisting of three magnetostrictive level sensors, an inclinometer and a central unit, that automatically performs the freeboard measurement, otherwise realized with manual meter readings, with large improvement of the measurement accuracy that is estimated around 1 mm. The level sensors have been battery powered and provided with a wireless connection to act as slaves of a Bluetooth piconet. The experimental results that show the functionality of the system and its great potential in extracting many useful information from the acquired data are also shown.