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Published online by Cambridge University Press: 18 January 2010
The seaman requires of radio aids to navigation that they should be effective substitutes for astronomical and terrestrial methods of fixing when these fail him, either wholly or in part. For normal peacetime voyaging there has been no firm demand for a radio system that will improve on the performance of the other methods at their best. The requirements for radio aids can therefore be related to the facilities which these other systems afford. This does not, of course, imply that circumstances do not exist in which radio aids can provide a degree of assurance that the other methods might not.