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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.
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>
>
>
> _____
>
> Get ideas on sharing photos from people like you. Find new ways to share.
> Get Ideas Here!
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>
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