海上における物標の視認と見張り

Abstract

The visual perception of the targets at sea is the most important factor for safety and for a good lookout in preventing marine disasters. The International Regulation for Preventing Collision at Sea, 1972 gives rules for a proper look-out (rule 5). What is a proper look-out? This study shows the conditions for the visual perception of the targets at sea in connection with the luminance difference threshold which is referred to the luminance of the sky (about 2 degrees over horizon). Author shows the visual conditions and factors thereof ; they are as follows ; 1. There is a physiological factor which masters and navigation officers on duty can't perceive by sight. 2. The condition for visual perception of the targets is more difference between the luminance of the sky and that of the target than the luminance difference threshold. 3. There are two psychological factors for a good lookout by sight. (1) Masters and navigation officers on duty should remember that there should be existing some targets in case of no sights of them. (2) They should have previous informations of the targets by using ARPA (Automatic Radar Plotting Aids) or RADAR (RAdio Detection And Ranging). 4. There are three physiological factors relating to the luminance difference threshold for a good lookout by sight. (1) They should maintain a proper look-out as long as possible. (2) In daytime, they had better use their sunglasses also in case of not feeling glaring, because of perceiving targets easily by sight. (3) They should use actually the binocular and compass for getting more informations with relative changing direction of targets.