Scanning sonar is an ideal tool for underwater search because it produces a “picture” of the underwater environment regardless of the water visibility.  It does this by sending out a sound wave that reflects off objects on the bottom or in the water column.  The reflected wave returns to the sonar head where it is received and sent to the surface for display.  The reflected sonar image is displayed on a laptop computer. 

Fishers SCAN-650 is a high performance scanning sonar system that can be mounted on an ROV, pole-mounted for use from a small boat in swallow water, or mounted on a tripod on the bottom.  The scanning sonar serves as an obstacle avoidance system and provides target identification.  The sonar beam sweeps in a 360 degree circle (or any portion of 360) allowing any object in the sonars “field of view” to be seen and displayed on the computer monitor.

In a typical application the sonar head or transducer is mounted on top of an ROV.  The head scans a circle around the ROV and “sees” targets in all directions, including those that are well beyond camera range.  The sonar images are displayed on the topside computer.  The operator, using the sonar for direction bearings, drives the ROV to the various targets for identification and videotaping. 

Scanned data files are stored on the PC’s hard drive along with boat’s GPS position, time, date, and other pertinent data. The recorded files can be played back at anytime.   Software is provided to allow post-processing of data including editing and merging of files. Small file sections, including screenshots, can be edited out and copied to a small file for emailing. A sizing tool is included in the software which allows the operator to determine the size of the targets on the screen.

The system package includes the sonar head with “downstairs” electronics, cable to surface, surface sonar processor, software, and a USB cable to your computer.

Scanning sonars operate very similar to radar, a signal is sent out from its antenna and then it listens for return signals. The signal is fan shaped and very narrow in width. The return echoes are displayed on the computer screen as a very narrow line that changes color along its length depending on the intensity of the echoes.

After the line is displayed, the antenna (called a transducer in sonar) rotates (steps) slightly to the right and the sequence is repeated. The smaller the step (1/2, 1, 1 1/2, or 2 degree) the higher the resolution of the picture. The transducer continuously steps, and the display quickly fills with the sonar image. The sequence is repeated, and if nothing moves (targets or sonar), then the identical picture will be overlaid over the previous picture (one line at a time).

The SCAN-650 uses a unique data transfer technique when transferring data between the scanning head and the upstairs sonar processor that cuts the time to complete a scan by as much as 50% over other manufacture's units; and it does it without any loss of data. Operating at twice the scan speed is very important when having to search large areas.

Fishers SCAN-650 is ruggedly built for commercial operations, and is covered by a full 2 year warranty.

• Up to 2,000 feet of cable: $3. per foot
• Carrying Case: $250.