Angled HR Profiler Deployment

I would like to measure current velocity and backscatter, particularly near the bed, in 15m depth, using an Aquadopp profiler that is strapped to a horizontal member of a bottom-mounted instrument frame.  Because significant turbulence will be generated by the frame and the many instruments attached do it, and because sediment will be scoured at the frame legs, I feel that it's appropriate to angle the profiler away from the frame, toward the bed, to get the measurements I need.  With a height above bed of 1.5m, angling the instrument at 45 degrees would give me a manageable profile length and measurement range (max tidal currents =0.3m/s).

My questions are:

1. Does this set-up make sense?  Is there a better way to do it?  Note that the profiler MUST be mounted to a horizontal pipe as mentioned above.
2. I always use BEAM coordinates.  Is that optimal here?

3. Any other tips?

Thank you for any advice.

John

1.  I think so, you'll just need to develop a custom transformation from beam coordinates to ENU or frame coordinates. I'm guessing you'll have a separate compass on the frame to tell you it's orientation and the Aquadopp will have a fixed orientation relative to the frame?

2.  The tilt sensors and compass won't work here (I think the max out at 30 degrees and the tilts here will affect the compass measurement as well) so you would want to use beam or XYZ. If the frame is stationary you should be fine using beam or XYZ, the only problem would be if the Aquadopp does any internal averaging and the frame is moving.

3.  If this is an HR Profiler you'll want to make sure you calculate distances to the boundary for each beam and see if the your pulse distance winds up shorter than any of these distances which will probably result in pulse interference.

P.J.