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Sonar for Search and Recovery ROVs

Rachel Doornekamp   |   March 31, 2020

There are a wide range of applications for Deep Trekker’s Remotely Operated Vehicles (ROVs) and crawlers. From aquaculture, commercial diving, ocean science and maritime industries to infrastructure , energy , municipalities and defense , Deep Trekker’s machines are versatile and capable.

In addition to these industries, Deep Trekker ROVs have proven themselves as effective and useful tools for Search and Recovery & Public Safety teams. Specializing in identifying targets of interest, victim and evidence recovery, and rapid search response, a Deep Trekker ROV enhances and assists search and recovery teams.

When time is of the most importance, Deep Trekker ROVs have eyes in the water in seconds. In time sensitive situations, the ROV provides real-time visuals quickly and safely. Tailor-made tools such as additional lighting or grabber arms allow teams to retrieve victims or evidence.

The easily transportable and deployable robots allow teams to work effectively in remote and difficult locations. In an industry as potentially dangerous as search and recovery, the assistance provided by an ROV helps to keep divers safe.

Murky water inherently is dangerous to navigate within. Below the surface, visibility can range from a few feet to a few inches away; in some cases, the water is so dark and dense you would not be able to see your hand, millimeters from your face. In conditions where visibility is dangerously low, murky water search & rescue operations are extremely difficult to perform. As it is impossible to ascertain the parameters of the dive area, safety becomes a greater concern for divers facing unknown and potential precarious conditions.

In turbid waters, the standard camera on the underwater drone will work similar to a human eye; they will have a hard time navigating through the water. This is where the navigational sonar systems come into play. From the surface, the ROV pilot navigates through the low visibility water solely using the sonar's heads up display (HUD); similar to how a pilot would rely on their plane's instruments when they fly through a fog. Add-on sonar allows for accurate and effective navigation and identification of targets in turbid or dark waters.

The benefits of pairing ROVs with sonar systems for search and rescue operations is clear. By using the sonar, either side scan sonar on a vessel or sonar directly on the ROV, you are able to quickly locate the objects or discrepancies underwater that may be the target you are searching for. From there, the ROV can be deployed to verify and retrieve, or help retrieve, the object.

Deep Trekker ROVs

Deep Trekker offers two submersible ROVs, the DTG3 and the REVOLUTION. Both vehicles offer operators with a convenient and straightforward way to get eyes underwater. Both equipped with a 4K camera, Deep Trekker’s ROVs provide users with high quality underwater footage.

The battery-operated vehicles are designed for ease of portability. Portability of an ROV is extremely important during a search and rescue mission. With bodies of water being located in some of the most remote locations on the planet, air transportation or on foot travel may be the only access. Deep Trekker vehicles come housed in their own convenient Pelican carrying cases, allowing them to be easily transported and deployed in isolated areas.

The DTG3 is a mini observation-class underwater ROV built to provide operators the ability to quickly deploy and visually inspect within underwater environments. Battery operated for up to 8 hours with a depth rating of 200m(656ft), the DTG3 is versatile and durable.

The REVOLUTION is a completely re-imagined ROV. The patented pending revolving head allows operators to rotate the camera, manipulators and sonar all while station holding in moving water. Depth rated to 305m(1000ft) with an 8 hour battery life (including quick swap), the REVOLUTION is tough and adaptable.

Ashton Davis, Houston County Rescue Chief and Board President shared that, “by far the best piece of equipment other than divers is this ROV,”

Sonar

Sound Navigation and Ranging (Sonar) technology is a system for the detection of objects underwater by means of sound waves sent out and reflected by those objects. Especially helpful for low visibility underwater operations when a camera system or diver would be unable to see clearly on their own, sonar is useful in a variety of applications.

Sonar has been used effectively by operators in various industries and working environments. Sonar technology has the ability to help locate underwater objects in operations where turbid waters may hinder maximum camera visibility. Perhaps most well known for search & recovery operations, sonar can help police and rescue teams locate evidence or victims underwater.

A big advantage of Deep Trekker and BRIDGE technology is the ability to integrate imaging sonars and USBL Positioning system data via our handheld controller. The display shows this data and allows you to record video, sensor data, sonar data and USBL data all as one. The USBL also allows for time stamped position data via a .csv file for easy interpretation after a dive. This eliminates the need for bulky setups with laptops and makes operations easier on the ROV pilot.

Deep Trekker offers a variety of sonar options. You can read more about the different types of sonar offered in What Can Sonar and USBL Do for You.

USBL Positioning

One option to consider that integrates with sonar is USBL. Ultra-short baseline, or USBL uses triangulation to indicate the position on the ROV. Consisting of a transducer at the surface and a transponder on the ROV, USBL is the closest thing to underwater GPS as possible. A relative position is plotted in a laptop generated software, this position can then be overlaid on maps such as Google Earth. Using a GPS coordinate from your computer or a device at the transducer, you can then estimate the GPS coordinate of the ROV within 20cm of accuracy.

As maps can be overlaid onto the software in real time, positioning and navigation is made even easier. Industries such as search & recovery use USBL systems to navigate large and potentially unfamiliar search areas. In short, having a USBL positioning system is extremely helpful for understanding where you are and where you are going under the water.

Side scan sonar

Side scan sonar comes in the form of a towfish or a side mounted sonar on a boat. While this option is not attached directly to an ROV, it is an important option to discuss as it is often a common option for search and rescue operations.

An ROV can work well with a side scan sonar, particularly in terms of target identification. After a side scan sonar has swept an area, the ROV can be sent in to quickly and safely identify points of interest.

Target Location

Before a successful recovery can be carried out, a search must be conducted to actually locate the target. Searches can be grueling and time consuming, with search areas often consisting of large areas and tough conditions.

The use of an ROV equipped with sonar provides recovery teams with a tool that allows them to safely and efficiently search large areas of water. Without the use of sonar on an ROV, teams typically send down divers to check an area section by section.

Given that someone has already been lost under the water, these brave divers are often placed in potentially dangerous or treacherous environments. Water depth can also be a limiting factor as divers have maximum depths that they are able to dive and decompression can be required. Depending on the water temperature and other external factors, dive times may be seriously limited.

In the summer of 2019, Houston County Rescue was dispatched to recover the body of Kelsey Starling following a tragic boat crash. The search took place in Smith Lake, Alabama, a man-made reservoir with depths of up to 300 feet. Using their DTG3 and sonar, the team was able to locate Starling. As the depths of the search area often exceeded 230 feet, divers would have had to spend nearly 3 hours decompressing for 45 minutes of searching. The DTG3 was able to dive all day to search, reducing risk and maximizing search time. In the summer of 2019, Houston County Rescue was dispatched to recover the body of Kelsey Starling following a tragic boat crash. The search took place in Smith Lake, Alabama, a man-made reservoir with depths of up to 300 feet. Using their DTG3 and sonar, the team was able to locate Starling. As the depths of the search area often exceeded 230 feet, divers would have had to spend nearly 3 hours decompressing for 45 minutes of searching. The DTG3 was able to dive all day to search, reducing risk and maximizing search time.

The use of a sonar equipped ROV is greatly beneficial in finding underwater targets in a safe, efficient and effective manner.

Target Identification

Once sonar has allowed an ROV to locate targets in the search area, the ROV can be used to identify these targets.

Lee County integrates the Deep Trekker ROV directly into their search and recovery procedures. After conducting witness interviews and testimonies to determine an appropriate area, the Lee County team uses sonar patterns on their boats to pick out targets underwater. Rather than suiting up and sending divers down to confirm the targets, the team sends an ROV into the water to review the targets in minutes. Once the victim or evidence has been found, divers either follow the tether to the target or the Deep Trekker ROV is used to retrieve the evidence.

“It’s not just our operations, it’s more of a regional asset for the state of North Carolina. It has sped up the process by which we find evidence, it’s increased the safety factor because we don't have to have divers in the water as much as before. Anytime you can take and use something mechanical or electronic to make it safer for our responders, it’s definitely a big asset to what we’re trying to do,” shared Shane Seagroves, Emergency Services Director of Lee County Government.

With the use of a sonar-equipped ROV targets can be identified quickly and safely to expedite the recovery process.

Target Retrieval

Sonar equipped ROVs are becoming more widely used in search and rescue missions to work in tandem with divers for target retrieval. As outlined above,once a target of interest has been identified and located using sonar and an ROV, divers can use the ROV and tether as a guide to reach the target or the ROV can pull the target up on its own.

This use of the ROV has been demonstrated in numerous cases. Perhaps most notably is the case mentioned earlier of Kelsey Starling, who was recovered in Smith Lake, Alabama. Smith Lake is a man made reservoir with trees of up to 90 ft in height covering the bottom making recovery difficult. After locating Starling, the team deliberately wrapped the DTG3 around the nearest tree to use as their diving guide line. Divers were then able to retrieve Starling quickly and safely by following the tether to their target. Ashton Davis, Houston County Rescue Chief and Board President noted that, “having the tether really helps recovery.”

You can learn more about the use of Deep Trekker ROVs in search and rescue missions by checking out our customer story with Special Agent Glenn Lang. Our industry experts are also here to help answer any questions you may have, reach out today!

If you’re ready to take the plunge and get a sonar-equipped ROV of your own, you can request your customized quote!