Synthetic-aperture sonar

Synthetic-aperture sonar (SAS) is a form of <a href="/facts/Sonar/0Rg2G40e">sonar</a> in which sophisticated post-processing of sonar data is used in ways closely analogous to <a href="/facts/Synthetic-aperture_radar/MJbDGvTh">synthetic-aperture radar</a>.
Synthetic-aperture sonars combine a number of acoustic pings to form an image with much higher along-track resolution than conventional sonars. The along-track resolution can approach half the length of one sonar element, though is downward limited by 1/4 wavelength.
The principle of synthetic-aperture sonar is to move the sonar while illuminating the same spot on the sea floor with several pings. When moving along a straight line, those pings that have the image position within the beamwidth constitute the synthetic array. By coherent reorganization of the data from all the pings, a synthetic-aperture image is produced with improved along-track resolution. In contrast to conventional <a href="/facts/Sidescan_sonar/jpSE1zxw">side-scan</a> sonar (SSS), SAS processing provides range-independent along-track resolution. At maximum range the resolution can be magnitudes better than that of <a href="/facts/Side-scan_sonar/jpSE1zxw">side-scan sonars</a>.
A 2013 technology review with examples and future trends is also available. For academics, the IEEE Journal of Oceanic Engineering article: Synthetic Aperture Sonar, A Review of Current Status gives an overview of the history and an extensive list of references for the community achievements up to 2009.
The length of the synthetic aperture is

 
 
 
 
 L
 
 s
 a
 
 
 ≈
 R
 η
 
 
 λ
 d
 
 
 
 
 {\displaystyle L_{sa}\approx R\eta {\frac {\lambda }{d}}}

Where R is the range, 
 
 
 
 λ
 
 
 {\displaystyle \lambda }
 
 is the wavelength at center frequency and d is the along-track element size in the array. 
 
 
 
 η
 
 
 {\displaystyle \eta }
 
 is a programmable parameter which controls the process beamwidth—the beamwidth actually processed.

Synthetic-aperture sonar open-in-new

Synthetic-aperture sonar