The Effectiveness Of A Color/saturation Beacon As A Navigational Range Indicator

Abstract

We evaluated the effectiveness as an aid to navigation a single- station beacon which was white when viewed from the centerline of a channel and became increasingly red or green when viewed from off center to the right and left. First we measured the observers' ability to determine whether a light was white, reddish, or greenish. A wide range of colors, from 575 nm to 585 nm, were judged to be white, making it difficult to specify a beacon that would adequately signal center of channel. Second, we measured the ability of the observers to detect a change in color for slowly changing stimuli. There were seven just noticeable differences in the range of color investigated. This would provide a sensitivity of 21.8 m (71.4 ft) over a 152 m (500 ft) wide channel. Measurements were taken with and without a 'white' reference light. Under no condition did the reference light improve performance. For changing stimuli, however, those that were brighter or larger provided better sensitivity than those that were small or dim.