Executive Summary
Sidescan sonar is one of the most misunderstood tools in maritime autonomy. Too many people treat it as a simple imaging sensor. It is not. It is a mission capability, and the level of that capability depends on the acoustic architecture, platform integration, survey speed, navigation quality, processing chain, and classification requirement.
Sidescan is like wine, if you ever try a high-quality wine, you can never go back…
A basic sidescan sonar can show you that something is on the seabed. A high-end synthetic aperture sonar can help you understand what that object may be, with enough fidelity to support serious operational decisions. That difference matters. Especially in mine countermeasures, route survey, seabed infrastructure inspection, and autonomous underwater vehicle operations.
Here is the uncomfortable truth: buying an AUV and adding a sonar does not create a mine-hunting system. It creates a vehicle with a payload. The mission starts when the payload can deliver the information needed at the speed, resolution, and confidence level required.
So let’s walk through five practical levels of side-scan sonar capability.
Level 1: Basic SingleBeam SideScan Sonar
This is the starting point. Think basic Marine Sonic-type side-scan sonar. Simple, effective, proven, and often very useful.
At this level, the sonar gives you acoustic imagery of the seabed. You can see wrecks, debris, cables, pipelines, rocks, tires, anchors, and sometimes objects that make your mine warfare people sit up a little straighter.
This level is excellent for search and recovery, basic survey, training, first responder work, port inspection, and general seabed familiarization. It teaches operators the fundamentals: shadows matter, altitude matters, stability matters, and bad sonar geometry creates bad interpretation.
But Level 1 has limits. The image may look fine, but beauty is not classification. A long shadow may indicate height. A bright highlight may indicate hardness. But you still need experience, context, navigation, and often another look. This is where many organizations fool themselves. They see an object on the seabed and say, “We detected it.” Fine. But detection is cheap. Understanding is expensive.
Level 2: AUV-Integrated SingleBeam SideScan Sonar
Level 2 moves the sonar from a simple towed or basic configuration into the AUV world. Think EdgeTech and Klein 3500-class systems integrated into autonomous underwater vehicles. The sonar images are much crisper and detailed compared to level 1.
Now the conversation changes.
The sonar is no longer just making pretty pictures behind a boat. It is part of an autonomous mission system. The vehicle must maintain altitude. It must hold a stable track. It must navigate accurately. It must collect data in a repeatable pattern. It must bring the sensor through the water in a controlled way.
This is a big step.
AUV-mounted sidescan sonar can reduce surface vessel dependency and improve access to areas where towing is difficult. It also keeps the sonar closer to the seabed, which can improve image quality and consistency in deeper water.
But there is a catch. The sonar is now fully dependent on the platform. Poor vehicle stability, bad altitude control, weak navigation, or poor mission planning will degrade the data. The AUV may look impressive in the brochure, but the seabed image will tell the truth.
At Level 2, the vehicle and sensor become one system. If they are not designed together, the mission suffers.
Level 3: MultiBeam SideScan Sonar for Higher-Speed Survey
Level 3 is where things become very interesting. This is the level of systems like Klein MANTIS UUV, using a more advanced multi-beam side-scan approach to deliver high-resolution imagery with improved area coverage.
The operational value is simple: better imagery at higher survey speed.
That matters because offshore operations are not academic exercises. Time offshore costs money. Time in a minefield costs risk. Time spent reacquiring targets costs patience, endurance, and sometimes political capital.
A traditional sidescan sonar often forces a trade between resolution and speed. Go too fast and image quality suffers. Push the range too far and classification confidence drops. Try to cover too much area and you may pay for it later with re-runs.
Multibeam sidescan changes that equation. It gives the operator more usable information across the swath and supports faster, more efficient surveys. For AUVs and UUVs, this is critical. Battery life, endurance, data volume, and mission time are always in negotiation.
Level 3 does not magically solve classification. But it raises the quality of the first look. And in real operations, the quality of the first look often determines how expensive the second look becomes.
Level 4: Entry-Level Synthetic Aperture Sonar
Level 4 is the start of synthetic aperture sonar. The Kraken SAS is a strong general-purpose example. Good value for money if you want to have a SAS sonar.
SAS is not just a better side-scan sonar. It is a different way of thinking about acoustic imaging. Instead of relying only on the physical aperture of the sonar array, SAS uses vehicle motion and coherent processing to synthesize a much larger aperture.
The result is high resolution over longer range, with more consistent image quality across the swath.
This is where sidescan starts moving from “I see something” toward “I can make a much better judgment about what I am looking at.”
For mine countermeasures, this matters. For seabed infrastructure inspection, this matters. For route survey, this matters. For any mission where the decision is more important than the picture, this matters.
But SAS is not free. It demands stable platform motion, good navigation, careful integration, serious processing, and disciplined survey design. Put SAS on a poor platform and you will discover that physics has a sense of humor.
Level 4 is a major capability step, but it requires respect.
Level 5: Multi-View Synthetic Aperture Sonar
Level 5 is where the game becomes operationally serious. This is where systems such as Thales SAMDIS 600 come in, using multi-view or multi-aspect synthetic aperture sonar to improve classification of mine-like objects in a single pass.
This is a big deal.
Traditional sonar imagery often gives you one dominant view of an object. But mine-like objects can be deceptive. A cylinder, rock, tire, cable crossing, biological feature, or piece of debris may look suspicious from one angle and harmless from another. Aspect matters.
Multi-view SAS attacks this problem directly. By providing multiple views or aspects in one pass, it gives the operator and the automatic target recognition chain more information about object shape, shadow structure, seabed interaction, and acoustic response.
In plain English: it reduces guessing.
That does not mean it removes the human from the loop. It means the human gets better information. It means the ATR has better features to work with. It means one pass can carry more classification value than a conventional survey line.
I call this the “Probability of Correct Classification”; and with a single pass, a skilled operator or ATR has about 35%-50% correct classification. With multiview, that goes up to 90%, which is a significant improvement.
For mine countermeasures, this is the direction of travel. The future is not just detection. The future is confident classification, reduced reacquisition, fewer unnecessary interventions, and faster decisions.
The Real Lesson
The five levels are not about brand names. They are about mission maturity.
Level 1 helps you see the seabed. Level 2 puts that capability on an autonomous platform. Level 3 improves coverage and speed. Level 4 brings synthetic aperture resolution. Level 5 adds multi-view classification power.
Each level costs more. Each level demands more from the platform, the operator, and the data chain. But each level also moves you closer to the real objective: useful information.
And that is where the industry needs to be more honest.
An autonomous underwater vehicle is not a mine-hunting system because someone bolted a sonar to it. A USV is not an MCM system because it can tow something. A beautiful waterfall display is not a classification decision.
The mission defines the sensor. The sensor defines the platform requirements. The platform only has value when it helps deliver the mission.
That is the part too many autonomy presentations skip.
Call to Action
If you are buying, building, or integrating autonomous systems for survey, MCM, or seabed security, ask one question before anything else:
What level of information do we need to make the decision?
Not what vehicle looks best. Not what payload fits easiest. Not what gives the nicest demo image.
Start with the decision. Then work backward to the sonar, the platform, the navigation, the processing, and the operating concept.
Because in underwater operations, the expensive mistake is not missing the target.
The expensive mistake is thinking you understood it.
Please comment so we can all learn from each other.
/Thomas
Originally published in the Strategic Pings ))) newsletter on LinkedIn on 2026-06-23. Subscribe there to get new editions first.