RE: [PSUBS-MAILIST] sonar question and safety at speed etc.

["Andrew Goldstein" <ag@desertstar.com>]

David,

Glad I can add to the discussion.  All of the various sonar technologies are very similar, the technology behind the medical ultrasound devices an an imaging sonar are almost identical.  The devils in the details.

What you can do safely depends upon the equipment available and your skill level.  I've been on large airliners which attempted to land in very dense fog (it took 4 very nervewracking attempts).  But this would be certain death in an ultralight.

I think certainly maximum speed will be dictated by conditions, but...

For the sake of argument say I absolutely had to make a high speed transit in low viz and all I had was a forward pointing depthsounder.  I would settle on the bottom, take a fwd scan, rise rotate a few degrees and take a scan, etc...repeat until I had a reasonable assurance that there was nothing in range and then proceed.   The range I could go at high speed would be limited to the range of my echo-sounder.   If I had a mechanically scanned sonar (probably an order of magnitude more in cost) then I wouldnt have to manual rotate the sub a few degrees,  I could just stop and let the sonar do it's thing, the images are pretty easy to interpret if your platform isnt moving.  

If I had a high speed imaging sonar ala Blueview then I could just fly, but the range of those imaging sonars is limited due to there high freq (so they have good resolution)

If I had a good map (side scan at the surface) and good nav (IMU, compass, etc.) I could transit at a relatively high velocity in zero viz,  The duration of high speed transits would be limited by the drift of the nav sensors and thus my confidence in my position on the map.

Hope that helps,

-a



> 
>   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




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