DIDSON™ Applications

Fisheries Management

Enumeration: DIDSON works in rivers and streams with rocky, uneven beds where other acoustic measurement products have been ineffective. DIDSON is generally placed in the water near the bank and looks perpendicular to the flow. Fish are imaged and optionally counted and sized as they pass through the sonar's field of view. When it is important to determine the number of fish around a particular structure, DIDSON can replace sampling nets by periodically counting the number of fish in a specific volume. Multiple methods for processing fish counts are available in the DIDSON software.

Fish Behavior: The near video quality of the DIDSON images allows observation of fish behavior in turbid water and at night near natural and manmade structures such as turbine intakes, fish screens, and the mouth of trawl nets.

Structure Inspection

DIDSON has been mounted on remotely operated vehicles (ROV), autonomous underwater vehicles (AUV), off the side of boats, and held by divers (DH model). The near video quality images allow detailed inspections of underwater structures. The DIDSON sonar has been used for manipulator feedback in turbid water and has allowed underwater work to continue when video cameras provided only blank screens.

Leak and Flow Detection

DIDSON can detect oil droplets or gas bubbles rising in water. This is useful for pipeline inspections. DIDSON can image small particles (1 mm in size) at ranges up to 3 m and can be used to monitor flow dynamics around objects.

Bottom Typing

Users can easily differentiate between rocky and sandy bottoms, determine rock sizes and density, determine plant sizes and density, and note details such as existence and dimensions of sand waves.

Search and Evidence Recovery

DIDSON can be used to help recover lost or discarded objects as well as examine underwater structures. If the search area is small, DIDSON can be used both for the initial search (low frequency mode) and the final identification and recovery (high frequency mode). If the search area is large, it can first be covered with a side-scan sonar which generates a map with bright marks indicating where there are large acoustic returns. The operators then prioritize the marks and go to those locations with an ROV, AUV, or a diver with a DIDSON to identify if it is a false target or the object of interest.

Hull and Berth Sweeps

DIDSON is used on AUVs, ROVs, and held by divers to search hulls and berthing areas. The Diver-Held version has a mask-mounted display with SVGA resolution that allows divers to see DIDSON images in real time while diving. The DIDSON images allow one to inspect hulls and berthing areas for damage, fouling, contraband, and improvised explosive devices in turbid water. Without this technology divers must resort to a search by tactile examination. The DIDSON allows objects to be identified from a stand-off distance that provides greater safety.

Underwater Surveillance

DIDSON works well as a component in harbor surveillance systems. In one, a low-frequency sonar surveys a large volume of water and alerts the operator to an approaching return that exhibits characteristics of a threat. The operator then directs a patrol boat to that location. When the patrol boat approaches the location, the crew lowers a DIDSON into the water and identifies the target as a diver, delivery vehicle, marine animal, debris or some other object. DIDSON can also be used to monitor an underwater location that needs high security, similar to the use of video surveillance cameras on land.

Vehicle Vision and Control

DIDSON can be placed on an ROV to aid in navigation and manipulator control. It can provide vision for the operator in environments where optical systems are ineffective. DIDSON can be used on the front of an AUV as a forward-looking sonar for obstacle avoidance and for filling in the gaps not covered by left and right side-looking sonars.