Synthetic aperture sonar on the HUGIN autonomous underwater ...

<strong>Synthetic</strong> <strong>aperture</strong> <strong>sonar</strong> on the HUGIN autonomous underwater vehicleContact persons:Torstein Olsmo Sæbø, tlf. 63 80 75 35 torstein-olsmo.sabo@ffi.noRoy Edgar Hansen, tlf. 63 80 76 36 roy-edgar.hansen@ffi.no3D imaging of the seafloor with interferometric synthetic <strong>aperture</strong> <strong>sonar</strong>Very high resolution mapping of the seafloor is of interest in areas such as underwater archaeology, search,mapping of dumpsites and mapping of offshore installations.Interferometric synthetic <strong>aperture</strong> <strong>sonar</strong> (SAS) can be used to produce maps of the seafloor with centimetreresolution. The HUGIN autonomous underwater vehicle (AUV) is equipped with a high resolution SAS.The scientific content in this work will be to develop new methods in SAS interferometry. The new methodswill be tested on data collected by HUGIN AUV.Multisensor fusion in seafloor mappingThe HUGIN autonomous underwater vehicle (AUV) carries both a multibeam echosounder (MBE) and aninterferometric synthetic <strong>aperture</strong> <strong>sonar</strong> (SAS) – both mapping sensors. By optimal fusion of the two different<strong>sonar</strong> technologies, reliable high resolution maps can be produced. This can be used in detaileddocumentation of the seafloor in various areas.The scientific content in this work will be to develop methods for fusion of MBE data and SAS data in highresolution mapping. The new methods will be tested on data collected by HUGIN AUV.Tomograpic imaging in synthetic <strong>aperture</strong> <strong>sonar</strong>The principle of synthetic <strong>aperture</strong> <strong>sonar</strong> is to increase resolution by increasing antenna size and therebyimprove resolution. By running in a circle around the area of interest, a tomographic image can be produced.This opens new possibilities in <strong>sonar</strong> imaging.The scientific content in this work will be to develop methods for circular synthetic <strong>aperture</strong> <strong>sonar</strong> imaging.The new methods will be tested on specific circular track data collected by HUGIN AUV.

Multiaspect synthetic <strong>aperture</strong> <strong>sonar</strong> interferometryA multiaspect interferometric SAS is a multidimensional oversampled sensor which produces data forcoherent spacetime array processing. By processing data from different views of the same area, newinformation about the area can be retrieved. This added information can either be used to improve resolutionor reliability.Applications for this are 3D rendering of objects on the seafloor (underwater archaeology, wrecks, offshoreinstallations).The scientific content of this work is to develop the concept of multiaspect interferometry, and the combinationof multiaspect shadow classification with interferometry for 3D rendering of objects (wrecks, installations) onthe seafloor.Multifrequency synthetic <strong>aperture</strong> <strong>sonar</strong> imagingScattering of acoustic waves from the seafloor is frequency selective. By using a <strong>sonar</strong> with large bandwidthin combination with frequency selective processing, specific information can be enhanced in the <strong>sonar</strong> image.This principle is used by dolphins and bats in classification of their targets.The scientific content of the work will be to develop multifrequency synthetic <strong>aperture</strong> <strong>sonar</strong> imagery, and todevelop techniques to assess frequency selective features in the <strong>sonar</strong> images. The techniques will be testedon ultrawideband <strong>sonar</strong> data collected by the HUGIN autonomous underwater vehicle.