Abstract
While conventional sidescan sonars are commonly used for seafloor imaging, they suffer from some basic limitations. Firstly, the imaging resolution, or the system's ability to distinguish closely spaced objects, is not constant but degrades with range. The angular resolution is roughly equal to the wavelength divided by D, where D is the aperture (receiver) length. Higher resolution is often desired, but to achieve that one has to either decrease the wavelength (increase the transmit frequency), or increase D (use a larger receiver array). There are practical limitations to both.
In synthetic aperture sonar (SAS), these limitations are overcome by using the sonar's movement to synthesize a long antenna, or aperture. The image resolution is significantly increased compared to conventional sidescan sonar. In addition, the resolution becomes independent of range and of frequency. SAS systems are typically carried by an autonomous underwater vehicle (AUV), and can achieve an image resolution of a few centimeters even in very deep waters.
This seminar offers an introduction to SAS, including key properties and limitations, and a glance at the processing sequence. Typical applications of SAS include searching for small objects on the seafloor, and monitoring of subsea structures such as oil pipelines. We will also show examples of potential new applications including imaging of bacterial mats related to fluid flow channels in the North Sea, and detection of bubble seeps. The examples shown in this seminar are from the HISAS 1030 interferometric SAS.
Presenter Bio
Ann E. A. Blomberg received her M.Sc. and PhD degrees in signal processing from the University of Oslo, Norway, in 2005 and 2012, respectively. From 2005 to 2008, she worked as a processing geo-physicist at CGGVeritas, Norway. In 2012, she was at the Centre for Geobiology (CGB) at the University of Bergen, working with sonar and seismic data acquisition, processing, and interpretation. She is currently a postdoc at the University of Oslo, working on a project entitled "Advanced sonar methods for detecting and monitoring marine gas seeps." As part of her postdoc, she will be working together with Thomas Weber as a visiting scientist at CCOM from December 2014 until the end of February 2015.
Publication Date
2-6-2015
Document Type
Presentation
Recommended Citation
Blomberg, Ann E. A., "An Introduction to Synthetic Aperture Sonar (SAS)" (2015). Seminars. 165.
https://scholars.unh.edu/ccom_seminars/165