Emergency Responders’ Uses of Sidescan Sonar
Many fire and police departments consider sidescan sonar an essential piece of equipment for their dive teams. Sidescan is used for search and survey operations because it produces detailed images of the underwater environment regardless of water clarity. In addition, the sonar is able to search large areas quickly, scanning several hundred feet of ocean, lake or river bottom with each pass of the boat, easily locating a variety of targets including sunken boats, submerged vehicles and drowning victims.
The sonar saves hours of search time and increases the safety factor. Towing a sidescan over an area produces a detailed map of the underwater terrain so divers know exactly what’s down there before entering the water. Even in zero visibility the images can be of almost photographic quality. Some sonar also allow vertical structures to be scanned by rotating the angle of the transducers on the towfish. This means a team can survey the face of a dam, seawall, pier, bridge support, or ship’s hull to look for damage or any “unnatural” device like an explosive that may have been attached to the structure. A significant number of state emergency management agencies and sheriffs departments have received homeland security grants to acquire this equipment to aid in the protection of ports and crucial infrastructure.
One of the agencies employing sidescan sonar is Wilmington Delaware’s Office of Emergency Management, USA. The agency’s first responders include members of both fire and police departments. The team keeps communications networks, transportation systems, infrastructure facilities, and vital public goods and services flowing. They were put to the test in 2012 when Superstorm Sandy battered the US east coast causing more than USD68 billion in damage and claiming the lives of 268 people. Having JW Fishers SSS-100K/600K sidescan allowed the team to search for missing persons, survey canals and waterways choked with debris, and inspect support structures of the many bridges crossing over waterways.
Another agency using sonar for infrastructure inspection is the North Carolina Department of Transportation which has vast responsibilities, including maintenance of the state’s 12,712 bridges. NCDOT purchased Fishers SSS-600K with adjustable transducers, which makes it possible for the sonar to scan vertical structures. With this capability the DOT can inspect the supports of any bridge that crosses over water, or survey an area prior to the construction of a new bridge. Owning the sonar allows the department’s engineers to perform inspections at a moments notice, instead of waiting for a contractor. Other key features of their system are a splashproof computer when operating the sonar from a small open boat, and mapping software which shows the track of the boat moving over the search area and the swath being scanned.
Military units around the globe, including the US Naval Explosive Ordinance Disposal Technology Division, are finding a variety of applications for sidescan. The division traces its origins back to WWII when there was an urgent need for countering advanced weapons systems of other nations. Current global events and evolving threats have reemphasised the importance of their mission for homeland defence and ongoing military efforts. EOD technicians are deployed worldwide and tasked with neutralising unexploded ordnance of any kind. Countering these threats requires they have quick reliable access to a broad range of tools and information. NAVEODTECHDIV determines which equipment and procedures are most effective for ordnance location and disposal. One instrument identified as extremely useful is sidescan sonar, and the division purchased several of JW Fishers SSS-600K sonar systems for this work. The 600K can scan a swath up to 150 metres with each pass of the boat and provides the high resolution necessary to identify small objects on the bottom, or in the water column. A number of European military units have also purchased Fishers sidescans for similar operations.
Image: Wilmington OEM first responders with JW Fishers sidescan; inset: European military officers with JW Fishers’ sonar.
