Forward Scanning Sonar
A forward scanning sonar would be great for an ROV or submarine
as it would give the ability to see what is out front long
before could otherwise see it and run into it. The cost is the
problem. JW Fishers www.jwfishers.com has a unit for about $6,500
It's a great unit, but the abilities and prices only go up from this point.
Side Scan Sonar
There are lots of high dollar commercial side scan units, but Hummingbird; www.humminbird.com, has brought sub $1000 side scan to the huge sport fishing market. Lowrance Structure Scan will add some competition to the low end market. These units are intended to work when mounted on to the bottom of a boat, but they can be modified to for us on a ROV or as a towed unit. Getting the transducer closer to the bottom improves the quality because the targets are closer and the tow fish and ROV are not rocking with every wave on the surface.
The transducers have successfully been down to 300 feet. How deep can they go? We'll have to find out.
Extending the Transducer's Cable can be done by simply purchasing
more cable. Hummingbird supports up to 50 feet, but the cable
has been extended to 300 feet with adequate performance.
Recommended, non-Hummingbird extension cable: Belden 9730 or
Alpha 6073C or any 12 to 15pf per foot.
Forward Scanning with a Side Scan Sonar
It's a bit more difficult to figure out what your looking at but
it is possible to rotate the side scan's transducer and get an
image. You can also block off one side and walk along the
shore with the transducer on the end of a pole.