An In-Situ Motion Measurement System for Underwater Sediments Tracking

This paper describes an in-situ motion measurement system called EcoSSGs, or smart sediment grains, with a specific application to measuring the motion of underwater sediments. EcoSSGs are gyro-free inertial measurement units (GFIMU) enclosed in a 4-cm-diameter, ceramic, waterproof sphere whose density resembles that of sand. They are placed in water to sense their motion in response to wave forces and record the data in their on-board memory card. After the experiments, the EcoSSGs are collected from water, and their data are transferred wirelessly through their enclosure to a host PC under the control of the user interface. We implement wireless reprogramming, wireless charging, and magnetic switching to support data and power transfer in a permanently sealed enclosure. Experimental results validate the ability to track the motion of sediments with high accuracy. We expect this system to be able to help researchers in fluidic dynamics and coastal engineering confirm their models of sediment motion underwater for the purpose of predicting coastline evolution and object motion in water in general.