A Draft Survey is a means of determining the weight of cargo loaded into or discharged from a vessel.
The draft survey measures the displacement of the vessel before and after cargo operations, with the resulting difference between the arrival and departure displacements representing the weight of the cargo.
In order to ensure the utmost accuracy, International Marine Survey personnel scrutinise several key variables, including:
- Water density within the dock, river or waterway
- Changes in the ballast condition
- Changes in the vessels consumables e.g fuel oil, drinking water, waste and slops.
- Trim corrections using the vessels hydrostatic data to account for her position in the water
The performance of an accurate Draft Survey is a skilled operation and should only be carried out by experienced professionals. Numerous external factors can effect the precision of the weight determined, from the sea conditions down to the clarity of the markings on the ships hull.
The raw data is then processed through a complex set of calculations and compiled into a draft survey report which you may use as a basis for certificating the quantity of cargo.