Question:

Can you explain the difference between commands DRAFT & DEPTH ?

Answer:

Both commands DRAFT and DEPTH set the waterplane level.

DEPTH sets the Origin Depth directly. Origin Depth is the shortest distance from the origin of the coordinate system (0,0,0) to the waterplane (measured perpendicular to the waterplane). This measurement is always valid regardless of the heel and trim angles.

DRAFT sets the Origin Depth (and possibly the trim also) indirectly. It specifies the draft at one or more longitudinal locations. Draft is always measured perpendicular to the baseline and in the centerplane. It is measured from the draft line which may be different from the baseline, but it is always perpendicular to the baseline. If the DRAFT command gives two or more drafts, it will also set the trim angle accordingly. If the DRAFT command gives more than two drafts, it may indicate a hogging or sagging condition.

DRAFT is not useful at large heel or trim angles because it is always in the ship's centerplane. For example, at 90 degrees heel the waterplane does not need to intersect the centerplane.