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Air Navigation Systems Chapter I. Astronomical Navigation in the Air 1919–1969
Published online by Cambridge University Press: 21 October 2009
Extract
As the marine sextant is only useful to low-flying aircraft because of its reliance on the sea horizon (see Section 1), many earlier pioneers descended almost to sea level to take their sights; but as Alcock and Brown were the first to discover, it is often necessary to climb above the cloud in order to see the sky. Some pioneers used the horizon of stratocumulus cloud below, among them K. M. Grieve who, with Hawker, would have been the first across the Atlantic if radiator trouble had not made them the first survivors of a mid-Atlantic aeroplane ditching. As Grieve was so happy with his cloud horizon, disbelief must be suspended. Indeed, what has been claimed to be ‘the first real aeronautical sextant’, designed in 1919 by the same ingenious Capt T. Y. Baker RN who invented the Baker Navigating Machine (see Section 4 5), used a reflecting prism as an index mirror and two horizon prisms giving a view of both the back and front horizons. Provided both cloud horizons were equally depressed below the true horizontal plane, the instrument gave the true altitude of the body observed.
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- Copyright © The Royal Institute of Navigation 1989
References
NOTES REFERENCES
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