The Metrication of Navigation

Abstract

In his original paper, Turner drew attention to the proliferation of units used to measure the same dimension. Granted the decision to adopt a metric system in this country, there could be no question but that SI was the correct one to adopt. It is not precisely the same as the traditional metric system at present in use on the Continent, but it seemed likely that it would become so, and, as the British Standards Institution pointed out, one change from Imperial to SI was far more logical than a change to traditional metric, followed by a change to SI.

SI avoids all the difficulties mentioned by Turner, but, as B.S.I, state (and Turner indeed infers in his statement that ‘speed (will be measured) in kilometres/hour’), we cannot abandon the hour and the day, which SI would require to be expressed as 86·4 kiloseconds and 31·4496 megaseconds respectively. Angle, too, presents a problem. The radian is quite irreplaceable in some mathematical fields but one cannot express a right angle or a complete revolution as a rational figure in radians. Horscroft revives the metric grade of one-hundredth of a right angle, but, as he points out, this logically demands a new basis for time measurement.