draft survey



A draft survey is a calculation of the weight of cargo loaded or unloaded to or from a ship from measurents of changes in its
displacement Displacement may refer to: Physical sciences Mathematics and Physics *Displacement (geometry), is the difference between the final and initial position of a point trajectory (for instance, the center of mass of a moving object). The actual path ...
. The technique is based on
Archimedes' principle Archimedes' principle (also spelled Archimedes's principle) states that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially, is equal to the weight of the fluid that the body displaces. Archimedes' ...
. The procedure is standardized by the
United Nations Economic Commission for Europe The United Nations Economic Commission for Europe (ECE or UNECE) is one of the five regional commissions under the jurisdiction of the United Nations Economic and Social Council. It was established in order to promote economic cooperation and i ...
for the measurement of coal cargoes.


The draft survey is performed by reading the ship's draft on the draft markings at six standard points on the hull: forward, midships and aft on both
port and starboard Port and starboard are nautical terms for watercraft and aircraft, referring respectively to the left and right sides of the vessel, when aboard and facing the bow (front). Vessels with bilateral symmetry have left and right halves which are ...
sides. Corrections for factors such as trim, water density and non-cargo weight changes are made before calculating the cargo weight change.


{{reflist Measurement Nautical terminology