Along-beam bin center separation

[PLACEHOLDER -- NEED TO CONFIRM THIS IS CORRECT AND/OR ADD PICTURE]

For ADCPs, the $Z$-axis in instrument coordinates is commonly defined along the axis of the ADCP pressure case. The velocity data are commonly given in terms of this $Z$-coordinate. For a vertical beam, the along beam bin center separation ($r_0$) is given by:

$r_0=z$

where $z$ is the distance from the transducer along the $Z$-axis.

For diverging beams, the along beam bin center separation ($r_0$) is given by:

$r_0=\frac{z}{\cos \theta }$

where $\theta$ is the angle of the diverging beams with the $Z$-axis.