A Calculate Cargo Weight with a Draft Survey: Determine the weight of cargo on your vessel using a draft survey method, measuring water displacement before and after loading/unloading. The difference in displacement reveals the cargo weight. Conduct the survey by reading draft markings at six standard points on the hull: forward, midship, port, and starboard. Account for trim, water density, and non-cargo weight like fuel and water. Accuracy relies on sea conditions during loading or discharge.