Synthetic Aperture Sonar Multi-aspect Differential Interferometry for Detection of Internal Waves

Refractive effects due to breaking internal waves can be present in synthetic aperture sonar (SAS) images and SAS bathymetries. These effects cause large linear structures (tens of meters by several meters) in the SAS images and may be misinterpreted as actual bathymetric features on the seafloor. Such misinterpretations limit our ability to acquire accurate knowledge of the seafloor and are therefore important to resolve. Detection of internal waves in SAS images using repeated passes has been suggested, but a robust detection method for single passes is still missing in the literature. We suggest a novel method which uses multi-aspect differential interferometry to detect these features caused by refractive effects. We present results from the MANEX’13 experiment, where internal wave effects where present in the SAS data and originally detected using multiple passes. We also include a reference dataset from outside Horten, Norway, where there are no indications of internal waves.