Dr. William H. Guier

Peer Reviewed

Abstract: THE EQUATIONS FOR DETERMINING range from an object using altitude (angle) measured from horizon to the top of the object are derived and compared with those given in Bowditch for Table 9, Distance by Vertical Angle. It is shown that the geometric approximations in Bowditch are valid for small vertical angles but can introduce significant errors for long ranges and large vertical angles. Furthermore, it is shown that errors caused by non-standard terrestrial refraction typically limit the accuracy over water to 0.1 nautical miles for long ranges. Finally, suitable tables equivalent to Bowditch’s Table 9 are included with extensions to smaller angles and lower objects, having in mind the particular application of small craft piloting.
Published in: NAVIGATION: Journal of the Institute of Navigation, Volume 15, Number 4
Pages: 366 - 375
Cite this article: Guier, Dr. William H., "NOTE ON DETERMINING RANGE FROM SEXTANT ALTITUDE", NAVIGATION: Journal of The Institute of Navigation, Vol. 15, No. 4, Winter 1968-1969, pp. 366-375.
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