Delft3D z calculation

[browniea]

Describe the bug:

Add a clear description of what the refence of z is.

The issue:

In the code d3d.py two function output the z location of data points ( get_layer_data and get_all_data_points ). The refence for this output needs to be clarified whether its the free surface or the zero water level.

[ssolson]

Did we switch this to a standard output?

Do we still want to add a new/ custom output?

[browniea]

Z is still calculated as "the depth from the zero-water level at the surface"

d3d.py lines 218-227

   if dimensions== 2:
        if layer_dim == 'FlowLink_xu FlowLink_yu': 
            z = [bottom_depth_wdim]-water_level_wdim
        else:
            z = [bottom_depth]-water_level
    else:
        if layer_dim == 'FlowLink_xu FlowLink_yu': 
            z = [bottom_depth_wdim*layer_percentages[layer_index]]-water_level_wdim 
        else:
            z = [bottom_depth*layer_percentages[layer_index]]-water_level

yes, I think instead of outputting z we want to output depth and move this to it's own function depth_zero_water_level

[ssolson]

From our discussion

• Currently get layer data returns x,y,z,variable
• Adjust to:
  • No custom z
  • no surface reference option in the function
  • Output water depth and water level always
  • water level is a constant in z-direction
  • water depth is variable by % of layer

[ssolson]

Addresses in #190