AIDS TO AIR NAVIGATION

Abstract

THE most reliable method of air navigation is by means of the celestial bodies. The time that can be devoted to training the air cadet in astro-navigation is necessarily limited. The air navigator can acquire all that he needs to know without much knowledge of mathematics, and can work more or less by rule of thumb ; but the, results are bound to be more satisfactory and the risks of error lessened, especially in an emergency, if he fully understands what he is doing. Prof. Deben-ham's little book has the commendable purpose of providing an easy approach to the principles involved by the use of graphic methods. A stereographic projection chart, with a matt celluloid rotatable disk, is provided to enable the spherical triangle to be solved approximately ; stereographic scales are also provided, which make a somewhat greater accuracy attainable. These graphical methods undoubtedly give a greater insight into what is being done than is possible by the routine use of mathematical formulæ, and the cadet who studies Prof. Deben-ham's volume with understanding cannot fail to benefit from it.

Astrographics, or First Steps in Navigation by the Stars

A Primer for the Airman Cadet. By Prof. Frank Debenham. Pp. v + 118. (Cambridge: W. Heffer and Sons, Ltd., 1942.) 7s. 6d. net.

The Observer' s Planisphere of Air Navigation Stars

By Ft.-Lieut. Francis Chichester. (London: George Allen and Unwin, Ltd., 1942.) 2s. 6d. net.