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Large Area Search and Recovery: How ROVs are Helping


What is Search and Recovery?

Search and recovery is the act of locating and retrieving a missing person when it has been determined that they are beyond rescue. Additionally, search and recovery includes the retrieval of valuable objects such as police evidence or overboard vessel equipment. Search and recovery is different from search and rescue, where search and rescue is the act of attempting to find a person suspected to be in distress or looming danger.

Search and recovery can occur in a variety of places, which include on ground locations such as forests, deserts or caves; as well as underwater locations such as lakes or oceans. In underwater search and recovery the goal is to find and retrieve the victim or object of interest. Retrieval can be performed by divers or remotely operated vehicles (ROVs).

Before a successful recovery can be carried out, a long, time-consuming, and often frustrating search is conducted. Effective operations are dependent upon the combination of extensive training, capable equipment, and organized field planning.

Search and Rescue Teams in Large Areas

Search and rescue (SAR) teams are made up of government branches such as local police, firefighters, military, and coast guards. Additionally, volunteers and other organized agencies, similar to the CASDDA Canadian Search and Disaster Dogs Association, work together to carry out these missions. The size and type of groups that partake in search and recovery operations depends on the mission’s objective such as the size of the location and the type of target.

To produce the best outcomes, the various parties have to complete extensive training where they learn about different search patterns and salvage techniques; as well as various navigation and communication strategies. Overall, training provides the best opportunity to recover the person or object of interest.

What are Large Search Area Tactics?

A large area of water that needs to be searched can be a lake or ocean. To accomplish an underwater search and recovery mission in a large area, there are a few underwater search patterns that can be used:

Tow Search Method

One method used to search a large area is the tow search method. In this method, up to two divers or cameras can be towed behind a vessel at extremely slow speeds as they inspect the area. Divers are towed using a towboard, which allows them to steer underwater. To begin a tow search, the vessel enters the area of interest and allows the diver to travel a safe distance from the boat. Once the diver has descended to the desired depth and signalled to the ship operator, the boat is slowly driven around a pre-planned path. When the diver finds something of interest, a marker is used to identify it for a thorough search later. If the diver finds the target, they can retrieve it if it is safe enough to carry. To keep divers safe, spotters are used and everyone is briefed on the search plan before entry into the water.

Tow Search Method Advantages:

  • The tow search method is a fast way to search a large area.
  • With thorough preparation, the tow search method can be used when there is zero-visibility underwater, as divers can use their hands to feel the bottom for anomalies.

Tow Search Method Disadvantages:

  • When using the tow search method, only highly trained divers should be utilized as substantial knowledge of the method and its safety procedures is necessary.
  • In certain steering positions, it can be hard to track points of interest effectively.
  • In poor visibility, divers will be far more limited than a side scan sonar to see the bottom.

Bottom Line Search Method

Another method to search large areas is using the bottom line search method. This method uses a team of 2-8 divers, who are dispersed along one rope. The divers use the rope to travel together along the bottom of the water body. The distance that the divers are separated along the rope is contingent on the visibility underwater.

Bottom Line Search Method Advantages:

  • This method allows for a speedy search of large areas.
  • In poor visibility, it is a bit easier to tell which areas have been searched.

Bottom Line Search Method Disadvantages:

  • The bottom line search method requires significant setup and coordination from divers.

Grid Search Method

Another method used to search large areas is using grids. When this method is utilized, numbered grids are mapped onto the body of water. The size of the grids will depend on the target of interest. Once the water is divided, divers or an ROV is assigned to a grid that is marked by buoys. Within the grid, a detailed inspection is performed and any findings are reported after examination. The grid method is hardly used in large area searches as it is a time-consuming process. It is usually employed when other methods have failed or there is a high likelihood of finding the target in a certain area.

This is the most common method when using a towfish or boat mounted side scan sonar. Side scan sonar works best when moving in straight lines. It is also best to overlap search lines as much as reasonably possible, at least 25-50%, to ensure that areas can be confidently “crossed off” as searched. The boat operator will drive the straight line, turn around and return back to overlap with the last line as closely as possible, while the side scan monitor on the boat is looking for anomalies that could be the victim. Anomalies are marked by throwing a floating marker in the vicinity of the target for further evaluation by diver or by ROV later.

Police with ROV

Variations of the Grid Search Method

The radius search method is a variation of the grid search method. It is very similar to the grid search method, however instead of square grid, circles are used. Additionally, the radius search method is commonly employed on water bodies with ice cover.

Grid Search Method Advantages:

  • An extremely accurate and comprehensive process.
  • The grid search method limits confusion when there are lots of divers that need to be dispatched.

Grid Search Method Disadvantages:

  • The grid search method takes a significant amount of time and equipment.
  • Only very experienced divers should be used due to the complexity of the method.
  • This method should only be utilized when attempting to locate smaller targets.

Read our article about sonars to learn what the technology is in more detail

Sonar Systems 101: All you need to know

What are the Benefits to Using an ROV in Large Area Recovery Efforts?

When a ROV is utilized in a large area search and recovery, the efficiency of a mission can improve as:

Improves Safety

One of the main challenges of search and recovery is the environment, often unpredictable or unknown; with cold temperatures, ice cover, wind and strong currents posing risk to the safety of the diver. ROVs are useful as they eliminate the need to send divers into dangerous conditions or unsafe areas.

However, when divers are needed, safety considerations must be addressed to ensure no additional loss of life occurs during the search. On top of diving in unknown and dangerous waters, these divers have limited oxygen tanks and search times. Given these circumstances, often ROVs can be used prior to sending a diver or in tandem to monitor the safety of the diver. ROVs improve safety for divers as they can be used to assess conditions underwater and identify any hazards to a diver, before they submerge underwater.

Improves Locating Abilities

In search and recovery, ROVs can be equipped with Sonar and USBL Positioning Systems that allow search and rescue teams to generate areas where the target of interest could be. Sonars are an extremely important tool for large area SAR teams, as the imaging sonar on a ROV can be utilized for the search effort as well as reidentifying targets from side scan searches or diver searches. In murky water scenarios, human eyes or high definition cameras are virtually useless to search an area. Sonar is a critical tool to improve locating abilities.

IMG 2782-min

Reduces Costs

ROVs are a more cost-effective solution to large area recovery efforts as they are less expensive than divers. Dive equipment, insurance, and training are all expenses that pile up over time for agencies that typically need to squeeze the most out of funding. ROVs provide a reliable ally for search and recovery missions while keeping humans safely above the water. Divers make excellent ROV pilots as well since they have a feel and understanding of the environments being searched.

Produces Quality Imaging

Having quality images is important in search and recovery as operators require a clear view of the water to identify their target. ROVs provide clear imaging through LED lights and HD live-camera feeds. In addition, ROVs are equipped with a camera that can rotate at various degrees allowing users to view the underwater environment at different angles. When performing a recovery, having a clear picture of the target and where to close the grabber is essential.

Easy to Transport

Search and recovery can occur in areas where it is difficult for a diver to enter. ROVs are portable meaning they can be brought and function almost anywhere. The long lasting batteries mean there is no need for a generator on site. This gives flexibility in hard to reach locations.

Reduces Time Spent

In search and recovery, reducing the time spent on a mission is important as it brings peace of mind to victims' families quicker. ROVs have quick deployment times allowing users to have eyes below the water in under 30 seconds. As well, ROVs can help complete a mission quicker as they withstand environmental conditions. Divers can slow down times as environment conditions and oxygen levels can limit the time divers spend underwater or increase the amount of breaks divers need.

Use ROVs to improve the locating, identification and retrieval of your target

Contact Industry Specialist

Cold Water Divers - Case Study

Mission Objective

In 2016, a British-Columbian based company, Cold Water Divers Inc. worked with a family and their team to help find their missing son, Ronnie. The father Ronald Sr., and the family were not giving up hope of recovering their son. The family wanted to locate their son Ronnie, as they wanted closure and a proper burial for him.

Details of the Mission

This mission took place over seven days on a frozen reservoir with each search day lasting about 14 hours. The search was done in conditions where it was always below freezing and temperatures reached around -15 degrees Fahrenheit (-26 celsius). To complete the mission, the team mapped out 18 holes that would be drilled into the twelve-inch thick ice. A heated tent was set up over the drilled hole, then the Deep Trekker DTG3 ROV was dropped into the hole. The DTG3 was utilized during the 14 hour search days to examine the bottom of the lake within the mapped out search radius.

Equipment Used

  • The Deep Trekker DTG3 ROV is an underwater robot equipped with an HD camera with 270 degree rotating head that enables operators to have a clear view of the surrounding environment. In addition, the DTG3 has automatic stabilization features, which allows operation in the harshest conditions. DT3G ROV Arctic Ice

Summary of Mission

Ultimately, the mission was successful. On the seventh day of the mission, the team began searching the twelfth hole. During the final hour of the mission, Ronnie was located after more than 3 square miles were searched. The family was able to bring Ronnie back to Texas and have a proper burial.

How Deep Trekker can be Used to Improve Large Area Search and Recovery?

ROVs are extremely useful in improving the cost, speed and safety of large area search and recovery. The DTG3 ROV, PIVOT ROV and REVOLUTION ROV are excellent ROVs to help at any stage of search and recovery mission. The ROVs help preserve crucial mission time as they have no topside power required allowing them to be deployed within 30 seconds. In addition, the ROVs can be equipped with sonar; as well as grabbers, which can be used in the retrieval stage. These ROVs can be easily brought anywhere, there have been missions conducted from watercraft as small as canoes.

Deep Trekker ROVs are used regularly on arctic and antarctic expeditions. In cold water operations, such as under ice missions, dive times for divers is extremely limited, the ROVs are proven in these environments as a long lasting cold water search tool.

If you are looking to add a ROV to your search and rescue team, our experts at Deep Trekker are happy to help find the appropriate technology within your budget.

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