I have a paper written by a Naval Architect consultancy on the accuracy of draft survey, which is public domain, which I have attached. We have permission to distribute the document since it is beleived that users should have no illusions about the accuracy of ships draft survey.
It was commissioned by CETOA, the the Coal Export Terminal Operators Association. In the case of coal, it said for old ships expect about 1% systematic error +/- 1% random, for the newer automated ships, about 0.5% +/- 0.5%.
A good belt weigher can do 0.25% pretty easily, draft survey is pretty rough really. Good belt weighers dont just happen however, many peoples/companies claim they can do them, few deliver.
L. Ian Burrell
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