Real-time SAS processing for high-arctic AUV surveys

Interferometrie Synthetic Aperture Sonar (InSAS) delivers ultra-high range independent image resolution with 3D seabed bathymetry at higher Area Coverage Rates (ACRs) and resolution than can be achieved with traditional physical aperture limited sidescan sonar. The along track resolution is achieved by synthesising the required aperture length by moving a physical aperture while sampling the field of view. The result is a compact power efficient solution ideally suited for use on Autonomous Underwater Vehicles (AUV) and towed platforms. This paper will discuss the advantages of SAS as a tool for search and survey applications, including a detailed analysis of the processing and data handling workflow. Example workflow steps include SAS processing (image and bathymetry formation), georeferencing, mosaicing, data formatting, map generation, data storage, data recovery and data visualization. In August 2014, Kraken Sonar Systems participated in the Victoria Strait Expedition to search for the missing ships from Sir John Franklin´s doomed Arctic expedition. The expedition team used a variety of sonar survey tools, including a Kraken InSAS system, installed onboard the Arctic Explorer AUV owned by Defense Research and Development Canada (DRDC). Results from the search will be presented, as well as a discussion of the application of AUVs for high-arctic seabed survey.