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Synthetic Aperture Sonar (SAS)
has long been accepted as the
“gold standard” tool available for
seabed mine countermeasure
missions due to its range and
effective resolution.
Meanwhile, access to SAS
capabilities has been effectively
democratized in recent years with
many options available in the
marketplace. However, there still
remains a long-running debate in
the subsea community around
the pros and cons of SAS versus
real aperture sonar such as multi-
aperture sonar (MAS) and
classical sidescan sonar (SSS).
Like most technical debates, the
right answer depends on the
mission, the environment, and
the confidence required in the
data. Many of the arguments
against SAS are rooted in
outdated assumptions that were
valid a decade ago—and are
increasingly irrelevant today.
Many of these perceptions come
from early generations of SAS
systems, when navigation
accuracy, onboard processing,
and power efficiency were
genuine constraints. Those
limitations shaped how SAS was
deployed—and, in some cases,
where it wasn’t.
Since then, advances in motion
compensation, computing power,
storage, and processing have
fundamentally changed what SAS
can operationally deliver.
Kraken Synthetic Aperture Sonar data of an offshore oil and gas
production field. Image: Kraken Robotics.
Shallow water is a notoriously
challenging sonar environment –
multipath dominates longer
ranges, thermoclines
(temperature variation) and
haloclines (salinity variations)
cause ray bending distortions,
and shallow depths dictate that
smaller, lighter weight underwater
vehicles are often chosen.
These same vehicles suffer from
increasingly dynamic motion
when sea state conditions
degrade.
All SAS systems rely on a
coherent combination of multiple
pings to form the synthetic
aperture, which relies on motion
compensation using navigation,
attitude and timing data.
Historical SAS sensors may have
relied upon highly stable
platforms and homogenous
environments, thus not being
suitable for shallow water
environments.
However, modern SAS has been
designed with the expectation
that real-world platforms are not
perfectly stable and incorporate
robust motion compensation
algorithms to account for
platform motion. For example,
Kraken SAS has a track record of
high motion tolerance and has
been demonstrated to work in up
to Sea State 6 in shallow waters.
Of course, even highly robust
SAS systems will eventually
SIDESCAN VS SAS
Myth 1: SAS isn’t Suitable for
Shallow Water Environments
SYNTHETIC A
DISPELLING
MYTHS
ABOUT