There are a large number of relatively inexpensive, small and easy to handle side-scans available. Most are usually restricted to shallow water less than 250 m. A frequency of 100 kHz is commonly used, which results in a wavelength of 1.5 cm and a minimum image resolution of about 0.25 m. The frequency can be changed without altering tow configuration or ship speed. Automatic, real-time data processing and equal-area registration of pixels commonly results in a very detailed acoustic image of the seafloor in shallow water.
Synthetic Aperture Sonar (SAS) systems are capable of collecting acoustic backscatter imagery with a high azimuthal resolution. The geometric operational requirements of the system demand a relatively slow tow speed or a reduction in the effective swath width. Not commercially available at present they have the potential to provide very high resolution seafloor images that could avoid optical surveys.
The parametric side-scan sonar is a dual frequency interferometric side-scan sub-bottom swath system. It can penetrate to tens of metres into the seafloor and is ideal for discerning dispersed or localised hydrate in the near seafloor zone.
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