This chapter examines the accuracy of the dynamic method of computing ocean currents as a function of the accuracy of physical measurement. The temperature of seawater at various horizons is usually measured with deepwater reversing thermometers. Modern deepwater thermometers have minimum scale divisions of 0.1°C. The reading accuracy of such a scale is ± 0.02°C. Temperature is read with an accuracy of ± 0.l°C from an auxiliary thermometer. A reduction correction is then introduced into the thermometer readings. The chemical method is the most widely used method in oceanology for determining the salinity of seawater from chlorine. The accuracy of determinations of the chlorine content in water depends on the accuracy of buret readings in the titration of samples of a given sea water and normal water. The allowable error in the titration of normal water can be neglected. The errors chosen are valid only for estimating the accuracy of the dynamic method.