This paper presents an approach to perform Simultaneous Localization and Mapping (SLAM) in underwater environments using a Mechanically Scanned Imaging Sonar (MSIS) not relying on the existence of features in the environment. The proposal has to deal with the particularities of the MSIS in order to obtain range scans while correcting the motion induced distortions. The SLAM algorithm manages the relative poses between the gathered scans, thus making it possible to correct the whole Autonomous Underwater Vehicle (AUV) trajectories involved in the loop closures. Additionally, the loop closures can be delayed if needed.
The experiments are based on real data obtained by an AUV endowed with an MSIS, a Doppler Velocity Log (DVL) and a Motion Reference Unit (MRU). Also, GPS data is available as a ground truth. The results show the quality of our approach by comparing it to GPS and to other previously existing algorithms.