Mike Hord wrote:
> Thanks for everyone's input.  It seems to me that some form
> of differential measurement is necessary.
> 
> Ultrasound is interesting but may make deployment of the
> instrument more complicated than people are willing to deal
> with.  Standard MO right now is to tie a rope or cable to it,
> toss it in the water and tie the other end to a large brick,
> tree, or post on the riverside.  Anything requiring precise
> orientation would likely turn people off.

What's so hard about getting correct orientation?
Rather than tying the long rope directly to the unit,
you attach it with a short extension length to the main rope.
That way the unit floats directly above the bend in the
rope, and with correctly shaped package, it always points
directly up (unless in strong current).
The fun part will be how well you can measure distance
to the surface.


    \SONAR/
     | G |
     | U |
     | T |
     | S |
     \Bat/
       O
       |
       |
       |
       +------To land line.
       |
       |
       T
       o
       |
       A
       n
       c
       h
       o
       r

Robert
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