Add option in `consolidate.add_depth` to use variables already in EchoData

[leewujung]

Right now consolidate.add_depth accepts only scalar inputs for input arguments depth_offset and tilt. However, these two variables can conveniently be DataArray with a time dimension. Or we may want to use the variables already stored in the EchoData object from which the Sv is derived from.

Relevant variables in the EchoData object are water_depth, vertical_offset, and tilt (AZFP only) all in the platform group.

This is required for the glider echopype-example notebook to plot the true depth.

Tasks

• ~allow accepting DataArray as inputs~ -- @emiliom and @leewujung that we will remove this requirement to make this function analogous to consolidate.add_location
• [ ] allow using variables already stored in the corresponding EchoData object
• [ ] add tests for the above cases

[emiliom]

@leewujung: AZFP data come with two tilt variables, tilt_x and tilt_y. I haven't been able to find unambiguous definitions of these two variables in ASL / AZFP documentation. What are the orientations of x and y?

consolidate.add_depth has a tilt argument. For AZFP data, how do we calculate tilt from tilt_x and tilt_y? Would the calculation always be unambiguous?

[emiliom]

I'm in touch with Steve and Julek (ASL) and have made progress with understanding tilt_x and tilt_y.

[emiliom]

Refer to #1051 for related discussions.