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Integrating Current Technology into Search and Recovery Operations

Search and recovery operations currently conducted by Fire and Law Enforcement Search and Rescue Teams often rely on outdated technology. Fish finders, inexpensive, low resolution sidescan sonars, and trained divers are the most used tools to search for downed planes, sunken ships, contraband, and missing persons. This application note will demonstrate an integrated approach using current, state of the art technologies in survey and inspection for search and rescue.

Seafloor Systems, Inc. manufactures, sells, and rents hydrographic survey equipment and complete systems. Our office is in the Foothills of the Sierra Nevada Mountain range due east of Sacramento, CA. In addition to being less than 2 hours from the San Francisco Bay area, Seafloor is surrounded by multiple lakes, reservoirs, and rivers that are largely fed by snowmelt from the Sierra. It is in these local lakes and rivers that many search and recovery operations conducted by local fire and Law Enforcement personnel take place. Seafloor has found that many of these agencies rely on an average of 15-year-old search technology, consisting of discontinued side scan sonars, fish finders, and ROV systems that are not working, not repairable due to end of life, or too complicated for their members to operate and interpret data from.

Technology in the Survey, Hydrographic, and Marine sectors has leapfrogged several times in the last two decades, producing more efficient, higher resolution, portable systems that are much easier to use, and much more affordable than their 10-15 year old predecessors. Seafloor Systems has been part of this evolution since our inception and has over twenty years’ of experience operating/renting/selling the available systems on the market. We integrate the best available tools to get the specified work done and meet the performance objectives within the allotted budget.

As a provider of hydrographic survey systems for conducting high-resolution bathymetric surveys, Seafloor has taken the initiative to integrate and utilize current technology on Search and Recovery (SAR) missions. In this sector, Seafloor utilizes multibeam echosounder technology as the primary search tool instead of a typical towed sidescan sonar system.

Sidescan sonar needs to be towed close to the bottom to produce usable results. This adds the complications of tow cables, potential snagging on underwater debris/trees, and a large amount of interpretation of sonar imagery results which only comes with repeat experience. Conversely, multibeam echosounders are deployed from a surface ship and can be configured to operate in 3D bathymetric mode, as well as backscatter modes, providing both 3D cloud points and 2D (Sidescan) sonar imagery from a single sensor. Interpretation of “objects” or “targets” is clear and intuitive to the untrained eye.

One example of utilizing multibeam instead of sidescan sonar occurred in 2019 in Sacramento, CA. A tow truck clipped the rear end of a tractor trailer, careened through a barrier, and fell 101 feet into the Sacramento River. It quickly sank 30 feet to the river bottom with two persons onboard. Local law enforcement using sidescan sonar and trained divers tried to locate the tow truck on the bottom of the mucky and fast flowing river unsuccessfully for two weeks. Coincidentally, a PG&E survey crew was surveying utilities and structures nearby on the bottom of the river using a Teledyne Reson SeaBat T50 multibeam echosounder. After inquiring about the ongoing search, the PG&E crewed offered to run their vessel over the site to try and locate it. In a single pass over the area (15-20 minutes), PG&E was able to definitively locate, identify, and pinpoint the vehicle’s exact location on the river bottom. A private recovery crew was able to recover the tow truck at that point.

Two weeks versus 20 minutes. Using multibeam sonar in this scenario would have resulted in significant savings of time, effort, and cost, as well as minimized diver-down time and maximizing personnel safety.

In May of 2021, a Seafloor Systems, Inc. crew was testing an Unmanned Surface Vehicle outfitted with a Teledyne Reson T-50 multibeam echosounder in Folsom Lake. While conducting calibration surveys, the team saw an irregularly shaped object on the lakebed resembling a small airplane in both the profile and backscatter modes.

To verify their findings, the team deployed a Seafloor SeaROVr (submersible remotely operated vehicle) outfitted with an Oculus forward-looking multibeam imagining sonar and live feed HD camera. Weighing 25 pounds, the SeaROVr was easily transited to the location by boat, then tossed overboard to investigate. Tethered by 275m of line, the battery-operated SeaROVr maneuvered to the lakebed, 160 feet below. The forward-looking sonar scanned the area and produced a 3D terrain model of the object, verifying beyond a doubt that it was a submerged plane. Additionally, the live-feed HD video camera relayed stunning images of the plane’s tail section and propeller back to the crew on the surface.

These examples demonstrate how efficiently the combination of Multibeam sonar technology and an ROV with sonar imagery and cameras can be used independently, or in conjunction with each other in SAR applications, to quickly identify targets of interest, and to direct divers more safely to ground truth or recover a target.

Multibeam sensors can also be deployed from an Unmanned Surface Vessel and navigate on preprogrammed track lines autonomously over an area or run routine surveillance lines around an asset without the cost and maintenance of a crewed survey/surveillance boat.

The cost savings from using the tool(s), need to be matched to the cost expenditures of the specific missions, goals, and rate of use. And with lower cost forward-looking sonar options to higher-cost Multibeam bathymetry options, or a combination of both, Seafloor is an ideal and experienced company who can help consult, identify, provide, and support the right approach for your missions.

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