Aquadopp HR Profiler pitch, roll and heading definitions

I have attached an image pulled from a Nortek manual, showing the type of head that is on our Aquadopp HR Profiler.

The x, y and z directions are clear from the diagram, but I'm unclear on how these translate to pitch, roll and heading (actually, I'm fairly confident about the heading, but I would like my guess to be confirmed).

Heading: When beam 1 is pointing north, the heading value returned by the internal compass will be 0 degrees, correct? 

Pitch: If you lifted the head end of the instrument upwards in the positive z-direction, this would change the pitch, correct? Would this be a positive or a negative change in pitch?

Roll: If you rotated the instrument around its x-axis, this would change the roll, correct? Let's say you rotated it such that beam 3 went upwards, while beam 2 went downwards--would this be a positive or a negative change in roll?

Finally, we'd be deploying the profiler with the beams pointing down, rather than as shown in the attached figure. I don't imagine this would change the meaning of the heading, but would pitch and/or roll directions be reversed?

Kevin Bartlett (logged on as Richard Dewey)

Thanks, Jonas. A very clear explanation and a useful diagram.