Page 39: of Marine Technology Magazine (April 2015)

SAS uses sophisticated signal processing techniques to com- data quality, better resolution and a pathway to a deliverable pare the multiple observations of the same area of sea? oor to of more integrated data fusion surveys.

calculate its depth. The image resolution of the seabed is sig- In addition to re? ectivity images, SAS can produce highly ni? cantly increased – often by an order of magnitude - com- detailed topographic maps of the sea? oor by detecting the an- pared to conventional sidescan sonar. In essence, the resolution gle of arrival of seabed echoes coming from a given range bin. becomes independent of range and of frequency. SAS systems In a con? guration known as Interferometric SAS (INSAS), can achieve an image and bathymetry resolution of a few cen- two vertically separated arrays produce bathymetric maps that timeters even in very deep waters. are exactly co-registered with the corresponding SAS images.

Figure 1 shows a simultaneously co-registered INSAS re- This combination of synthetic aperture processing and inter- ? ectivity image and 3D bathymetry of discarded automobiles ferometry solves the problems of limited resolution and cov- in Halifax, Nova Scotia collected during sea trials with the erage rates encountered with conventional swath bathymetric

Defence Research Development Canada. sonars and multibeam echo sounders. When the InSAS bathy-

While SAS has been around for over a decade, military ap- metric resolution approaches that of the corresponding SAS plications such as naval mine countermeasures have been its image, it becomes possible to overlay the re? ectivity and to- major development driver. However, SAS is a multi-use tech- pography to create a true 3D picture of objects on the seabed. nology with great potential for offshore oil and gas survey- The use of INSAS systems – such as the AquaPix system ing, hydrographic surveys, underwater archaeology, benthic produced by Kraken Sonar Inc. - is a promising tool for habitat mapping and deep sea mining. The viability of SAS achieving these objectives in both very shallow water and as a high resolution survey sensor seems a logical progres- deep water environments. AquaPix® produces real-time, high sion for the industry with the additional bene? ts of increased resolution, three dimensional (3D) digital terrain models of

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