Mapping Underwater Terrain with an Autonomous Boat

Researchers at the University of Texas at El Paso (UTEP) have developed an unmanned surface vehicle (USV) that can conduct bathymetric surveys on bodies of water. The goal of the project was to build a robotic device that can autonomously survey lakes, eliminating the need for a crew of individuals to conduct the task. This helps save man power, energy, and overall provides a safer method for conducting bathymetric surveys. The work was published in the May issue of the journal Sensors.

Laura Alvarez, Ph.D, the lead author of the work states, “Scientists need underwater maps in order to understand water bodies such as lakes, rivers, oceans, and reservoirs. So underwater maps can be used to understand how much water is in a reservoir and can also be used to detect hidden objects underwater.” Furthermore, bathymetric surveys play an integral part of oceanic sciences, management of water resources, hydrologic modeling, flood forecasting, and the studies of vegetation and aquatic ecosystems.

Alvarez is an assistant professor at UTEP and began developing the autonomous boat several years ago. However, Fernando Sotelo, a master’s student in electrical engineering picked up the work on the boat as part of his master’s thesis. His goals included not only optimizing the system but creating a reliable, economic, and self-powered autonomous system. The USV is constructed using a lightweight aluminum structure that sits upon an inflatable tube and consists of three main subsystems that are navigation, guidance, and control.

For the navigation subsystems, propulsion is achieved with four T200 thrusters that allow it to turn, move in a straight line in forward and reverse, and prevent roll and pitch movements. The guidance system features a combination of Mission Planner software which plans and loads autonomous missions into the vehicle and a flight controller. The flight controller acts as the brains of the system, communicating with the onboard sensors, speed controllers, telemetry modem, and GPS. Using a combination of the GPS along with a digital compass the USV knows where it is at and can determine the distance and direction of the next location it needs to go. Furthermore, four antennas on top of the device transmit real-time information back to a ground control PC for live monitoring and real-time status. Lastly, the control system consists mainly of a RiverSurveyor M9. This is an acoustic current doppler profiler that allows the USV to measure three-dimensional water currents, depths, and bathymetry. A Raspberry Pi was also included in the system to help monitor critical signals, control the power system, and operate a fail safe system.

A proof of concept test was done at Ascarate lake in El Paso in which the USV created 2D and 3D maps for small portions of the lake. The USV is planned to be put to use this summer mapping out the Rio Grande River’s flow and depth. With the current battery and solar system employed onboard, the USV is estimated to get up to four hours of continuous runtime. More information including instructions on how to build the device are available in the Sensors publication. “The reason we wrote the paper was so that anyone can reproduce it themselves,” Alvarez said. “It serves as an effective guideline to get them started.”