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I only ment that the images I had seen of sidescan sonar seemed a lot like looking into a womens insides for the sex of a yet born child using "ultrasound". (I would like to correct that which I was in reference to at this point in this thread.) I seem to have a much better handle on passive or listening sonar, but I am interested in the active portion as well. The best example I have been exposed to as to this side scan sonar, was a short documentary on how the "Liberty Bell 7" space capsule was located and identified against many other unknown submerged objects offshore. I would like your opinion as it relates to the following: There are times that the visability can be extremely short due to clouded water. During these periods, how would you recomend one safely commute near the bottom besides obviously going very slow in speed. Is there an afordable active sonar that could render a "picture" of what lies ahead or within your boats path that is fairly easy to interpret? Your explaination of these types of sonar has been very interesting. Thank you for having shared these with us. David Bartsch > Date: Wed, 27 Aug 2008 06:21:57 -0700 > From: ag@desertstar.com > To: personal_submersibles@psubs.org > Subject: RE: [PSUBS-MAILIST] sonar question and safety at speed etc. > > All, > > Thought I'd chime in. > > David, If by ultrascan you meant ultrasound (like for medical imaging, looking at a foetus etc.) then > a multibeam imaging sonar like Blueview or Farsounder or DIDSON is closer. If you meant ultrascan (like the trade name for > some NDT equipment I think) then a side scan is kinda similar to an B-SCAN device (any NDT speciallitst feel free to correct me :) . Jay's description of a sidescan sonar is essentially correct. If you meant something else, perhaps you could educate me. > > There is another class of active imaging sonars, scanning sonars, that are similar to a side scan in that they use as single narrow beam, but the transducer head rotates to generate the image (rather than towing a fish). This is very similar to a sector scanning radar. These give the user pretty good operational awareness but the images are often very difficult to interpret if used on a fast moving platform. (Imagenex, Tritech, Kongsberg Mesotech are suppliers) > > There is also a passive acoustic technology that can be used, although as far I know it's only been in the lab. This is acoustic daylight imaging, ADONIS (http://extreme.ucsd.edu/Research/AcousticDaylight/AcousticDaylight.html). This is really cool, the idea is that the ocean is in general a noisy place, (bubbles, snapping shrimp, boat motors, etc.) and everything reflects or absorbs this sound. So it is "theoretically" possible to capture ambient acoustic energy through a large array and parabolic receiver and make an image. The main problem is that the wavelengths are so long that the device gets pretty large and resolution is a bit of a problem, not to mention computer processing power. But they did get it to work somewhat in the lab and some field trials. > > All that being said, none of these sonar technologies is really adequate for insuring safety if you are moving to fast. They all suffer to differing degrees with problems such as range, resolution, acquisition time, difficulty in interpreting imagery, etc. Although the FarSounder or Blueview is probably closest to what you would need. > > If you did have a real need for moving fast near possible obstructions (like you are doing seafloor mosaicing over a large area) It would be very prudent to first do a sidescan or similar similar survey from the surface to detect objects that may cause problems. > > -a > > > > > -----Original message----- > From: "Jay K. Jeffries" bottomgun@mindspring.com > Date: Wed, 27 Aug 2008 11:00:19 -0700 > To: personal_submersibles@psubs.org > Subject: RE: [PSUBS-MAILIST] sonar question > > > David, > > > > On reflection, ultrascan is similar to side scan. > > > > R/Jay > > > > > > > > Respectfully, > > > > Jay K. Jeffries > > > > Andros Is., Bahamas > > > > > > > > Talk sense to a fool and he calls you foolish. > > > > - Euripides (484 BC - 406 BC) > > > > > > > > From: owner-personal_submersibles@psubs.org > > [mailto:owner-personal_submersibles@psubs.org] On Behalf Of David Bartsch > > Sent: Wednesday, August 27, 2008 6:34 AM > > To: personal_submersibles@psubs.org > > Subject: RE: [PSUBS-MAILIST] sonar question > > > > > > > > Thanks for your answer...you can see how I could have seen this as such > > concidering the image these produce. > > > > > > David Bartsch > > > > > > > > _____ > > > > > > From: bottomgun@mindspring.com > > To: personal_submersibles@psubs.org > > Subject: RE: [PSUBS-MAILIST] sonar question > > Date: Wed, 27 Aug 2008 06:12:40 -0400 > > > > > > > > David, > > > > Side scan simplified is just two bottom sounder units turned on their sides > > with an array of transducers to form a narrow beam. A past member of this > > list has (had) a great web site depicting how to build one with two > > economical Hummingbird units and 8 puck transducers (4 pucks per side wired > > in series-parallel configuration). With the advent of the economical > > Hummingbird (Model 997 ???) side scan unit that Carsten has described on his > > web site, home-built becomes moot for the power of this unit. Just build a > > fish and add some cable to have a very powerful unit. > > > > > > > > It is not an ultrascan unit. > > > > R/Jay > > > > > > > > Respectfully, > > > > Jay K. Jeffries > > > > Andros Is., Bahamas > > > > > > > > Talk sense to a fool and he calls you foolish. > > > > - Euripides (484 BC - 406 BC) > > > > > > > > From: owner-personal_submersibles@psubs.org > > [mailto:owner-personal_submersibles@psubs.org] On Behalf Of David Bartsch > > Sent: Wednesday, August 27, 2008 3:35 AM > > To: personal_submersibles@psubs.org > > Subject: [PSUBS-MAILIST] sonar question > > > > > > > > A question about side scan sonar....Is side scan sonar essentially an > > ultrascan machine designed to work in the ocean? I just was just curious. > > > > > > David Bartsch > > > > _____ > > > > Get ideas on sharing photos from people like you. Find new ways to share. > > Get Ideas Here! > > <http://www.windowslive.com/explore/photogallery/posts?ocid=TXT_TAGLM_WL_Pho > > to_Gallery_082008> > > > > > > > > _____ > > > > Get ideas on sharing photos from people like you. Find new ways to share. > > Get Ideas Here! > > <http://www.windowslive.com/explore/photogallery/posts?ocid=TXT_TAGLM_WL_Pho > > to_Gallery_082008> > > > > > > > > > > ************************************************************************ > ************************************************************************ > ************************************************************************ > The personal submersibles mailing list complies with the US Federal > CAN-SPAM Act of 2003. 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