Richard F. Haines and William H. Allen

Peer Reviewed

Abstract: THE IRRADIATION PHENOMENON has the effect of displacing the apparent edge between a bright area and a darker area toward the latter. One method of quantifying this effect is by determining the minimal angle of resolution (MBR) between a point source and an extended bright source. This paper presents the results of a series of investigations on the MAR between a point and an extended circular source and between a point source and a simulated horizon. The apparent angular diameter of an extended circular source is also quantified. A total of 11 highly trained male observers took part in the studies reported here. -411 had 20 : 20 distance acuity. Each observer moved a point source along various frontal plane meridians behind an extended source in order to determine at what position it became invisible due to the effects of irradiation. Results indicated that (1) the apparent edge of high luminance targets can be displaced as much as 15’ arc from the target’s actual edge under some viewing conditions, (2) the MBR is a function of the contrast ratio between the target and background and the luminance of the point source, and (3) the detrimental effects of irradiation are not reduced by using optical filters across the entire field of view to reduce the luminance of the extended source. The findings are related to certain aspects of manual navigation presently in use.
Published in: NAVIGATION, Journal of the Institute of Navigation, Volume 15, Number 4
Pages: 355 - 363
Cite this article: Haines, Richard F., Allen, William H., "IRRADIATION AND MANUAL NAVIGATION", NAVIGATION, Journal of The Institute of Navigation, Vol. 15, No. 4, Winter 1968-1969, pp. 355-363.
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