[PSUBS-MAILIST] Forward scanners

[Sean T. Stevenson via Personal_Submersibles]

What you probably want is a sector scan sonar. This employs a horizontal beam that sweeps 360° around the boat, giving you the best situational awareness, and is easy to interpret. This would be in conjunction with a single transducer altitude indicator.

If you actually wanted to automate navigation, then a DVL (Doppler velocity log) is probably in order. This is a four beam system which gives you differential movement, but the last time I checked was $15 K or so.

I might look at a unit like this:

http://www.imagenex.com/html/881l-gs.html

Sean


On October 8, 2014 3:55:08 AM MDT, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>Has anyone had any experience or know anything about forward
>scanners.I'm reading.....Without moving parts, the ForwardScan
>transducer is more akin to a conventional sounder that has been tipped
>on its side. Its effective range is about eight times the actual depth,
>up to about 160 feet ahead of the boat. It includes a built-in shallow
>depth alarm with parameters set by the user. In deep water, this is
>great for detecting rocks and pinnacles. Of course, if you are
>operating in shallow waters such as the Bahamas or portions of the
>Chesapeake the eight-to-one ratio begins to work against you.This seems
>to indicate that if you are cruising 5ft off the bottom or closer in a
>submarine, you won't get much warning for collision avoidance from the
>alarm settings These would just pick up on the bottom 5ft below rather
>than an obstruction coming off the bottom in the distance. Can these be
>mounted so the angle of the beam runs parralel to the sea bed, pointing
>more up than down? Or do I leave as is & forget about the alarm
>function. Am I just as well off buying a fish finder & mounting that
>forward facing? Regards Alan.
>
>
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