Page 34: of Marine Technology Magazine (March 2016)

Sea? oor Mapping

In reality, however, the logistics of manufacturing and de- angle of arrival of seabed echoes. In a con? guration known ploying an array of that size is impractical. SAS overcomes as Interferometric SAS (INSAS), two vertically separated ar- these limitations by using the platform’s trajectory to increase rays produce bathymetric charts that are exactly co-registered the data resolution. The forward motion of the sonar is used with the corresponding SAS images. This combination of to synthesize an array that is much longer than its physical synthetic aperture processing and interferometry solves the length by combining multiple pings in software rather than inherent limitations of low resolution and area coverage rates relying on costly hardware. encountered with conventional swath bathymetric sonars and

SAS uses sophisticated digital signal processing and motion multibeam echo sounders.

compensation techniques to compare multiple observations of While SAS has been around for over a decade, military the same area of sea? oor. The image resolution of the seabed applications such as naval mine countermeasures have been is signi? cantly increased – often by an order of magnitude. In its major development driver. However SAS is a multi-use essence, the resolution becomes independent of range and of technology with great potential for offshore oil and gas sur- frequency. SAS systems can achieve imagery resolution of a veying, hydrographic surveys, underwater archaeology, ben- few centimeters even in very deep waters. thic habitat mapping and deep sea mining. Reducing the cost

In addition to re? ectivity images, SAS can produce highly and complexity of marine survey operations can profoundly detailed hydrographic charts of the sea? oor by detecting the impact the economics of many marine industries. Driven by

The Seagull Unmanned Surface Vessel from Elbit Systems can be ? tted with Kraken’s

KATFISH sonar payload for mine countermeasures and underwater intelligence, surveillance and reconnaissance missions.

March 2016 34

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