Title
Shadow Enhancement in Synthetic Aperture Sonar Using Fixed Focusing
Author
Groen, J.
Hansen, R.E.
Callow, H.J.
Sabel, J.C.
Sæbø, T.O.
TNO Defensie en Veiligheid
Publication year
2009
Abstract
Abstract—A shadow cast by an object on the seafloor is important information for target recognition in synthetic aperture sonar (SAS) images. Synthetic aperture imaging causes a fundamental limitation to shadow clarity because the illuminator is moved during the data collection. This leads to a blend of echo and shadow, or geometrical fill-in in the shadow region. The fill-in is most dominant for widebeam synthetic aperture imaging systems. By treating the shadow as a moving target and compensating for the motion during the synthetic aperture imagery, we avoid the geometrical shadow fill-in. We show this to be equivalent to fixing the focus at the range of the shadow caster. This novel technique, referred to as fixed focus shadow enhancement (FFSE) can be used directly as an imaging method on hydrophone data or as a postprocessing technique on the complex SAS image. We demonstrate the FFSE technique on simulated data and on real data from a rail-based SAS, and on two different SAS systems operated on a HUGIN autonomous underwater vehicle.
Subject
Physics
Underwater acoustics,
Beamforming
Focusing
Imaging
Shadow
Synthetic aperture sonar (SAS).
To reference this document use:
http://resolver.tudelft.nl/uuid:e8c46fd1-cdc5-46b7-8677-972d28da0898
DOI
https://doi.org/10.1109/joe.2008.920996
TNO identifier
347371
Source
IEEE Journal of Oceanic Engineering, 34 (3), 269-283
Document type
article