DIDSON™ Applications

Fisheries Management

Enumeration: DIDSON works in waterways with rocky, uneven beds where other acoustic measurement products have been ineffective. DIDSON is generally placed in the water near the bank and pings 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 images allow detailed inspections of underwater structures. The DIDSON sonar is used for manipulator feedback in turbid water and allows underwater work to continue when video cameras provided only blank screens.

Leak and Flow Detection

DIDSON detects oil droplets and gas bubbles rising in water. This is useful for pipeline inspections. DIDSON can images small particles (1 mm in size) at ranges up to 3 m and visualizes flow dynamics around objects.

Bottom Typing

Users 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 helps 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, a side-scan sonar 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 the mark.

Hull and Berth Sweeps

DIDSON can be mounted on AUVs and ROVs or 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 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. As an example, 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 mounts on an ROV and aids in navigation and manipulator control. It can provide vision for the operator in environments where optical systems are ineffective. DIDSON also mounts 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.