Surveying bodies of water accurately is a challenging task. Authorities and port operators are required to provide up-to-date maps of riverbeds and port facilities. Until now, this has required the use of special mapping vessels and a great deal of manpower. It is costly and is not being carried out with the frequency and precision that will be required for future applications, such as autonomous shipping. For this reason, a team of researchers at the Fraunhofer Institute of Optronics, System Technologies and Image Exploitation IOSB has developed an easy-to-operate, unmanned watercraft that autonomously surveys bodies of water such as rivers, lakes, and harbors both above and below the surface and produces corresponding 3D maps.
Using its GPS, acceleration, and angular rate sensors, and a sensor called a Doppler velocity log (DVL) that enables the boat to incrementally feel its way along the bottom of the body of water, the vessel can move autonomously. The data from the various sensors are merged to guide the semi-automatic navigation system. For mapping above water, laser scanners and cameras are used in combination with mapping software developed at Fraunhofer IOSB, enabling the devices to reconstruct high-precision 3D models of the surroundings. The underwater mapping, in turn, is carried out with the help of a multibeam sonar, which is integrated into the sensor system and creates a complete 3D model of the bed. “Our navigation system is semi-automatic in that the user only needs to specify the area to be mapped. The surveying process itself is fully automatic, and data evaluation is carried out with just a few clicks. We developed the software modules required for mapping and autonomous piloting,” explained Janko Petereit, a scientist at Fraunhofer IOSB.
