Often this will be achieved by ‘shore measurement’, from which a ‘bill of lading weight’ is obtained, and on which freight is based. Sometimes, though, shore instruments are suspect – perhaps non-existent – and cargo/bill of lading tonnage – ‘intaken weight’ – is calculated by means of ‘ship’s draft survey’. In some trades there may be a discrepancy between shore cargo figures and cargo intaken quantity estimation as assessed by ship’s draft survey. Provided such discrepancy is of relatively minor proportions, the problem may not be serious but, given the high value of certain commodities, a substantial difference between these two sets of figures calls for immediate and closer investigation. On some occasions, freight is to be assessed on ‘cargo outturn quantity’ at the port(s) of discharge and again, this quantity may be calculated by means of shore gauges or by ship’s draft survey. Where ‘draft surveys’ are involved, often a charterparty will include a clause specifying that the surveyor will be independent and also that the ship’s officers are to provide every assistance to the surveyor to the extent of providing ship’s plans and refraining from pumping water or bunkers during the survey itself. In certain trades – e.g. for iron ore – where cargo is liable to suffer from weight loss (due principally to the evaporation of moisture) during transit, it is common to give charterers the option to abide by loaded figures on which to base freight calculations, or to weigh the cargo upon its discharge. As a further alternative, a charterer may negotiate the right to deduct from freight a percentage off the bill of lading weight obtained at the loading port – say 0.5% – ‘in lieu of weighing’ cargo upon discharge. In most trades this is now an option which is rarely exercised but the clause survives and so the 0.5% becomes just another ‘picking’.