Simply put, draft surveys are any calculations or studies carried out, which record the draft of a vessel for the primary purpose of measuring its weight in any condition of loading. These provide important results and conclusions about the hydrostatic forces, as well as aiding in draft surveys.
The draft (denoted by T), the length between the fore and aft perpendicular, referred to as the length between both perpendiculars (Lpp or Lbp), and the vessel’s breadth at the upper deck (B) are commonly taken as the principal standard dimensions of a vessel.
The draft of a vessel (spelt as draft in the American system or draught in the British system) is a measure of the distance between the surface of the water which meets the hull of the vessel, commonly termed as the waterline, and the keel or baseline of the vessel, which is the lowest member running in a longitudinal direction that provides support and structure to the shape of the hull.
