導標による位置の線の精度

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Leading beacons are simple to see but they offer a good position line. There seems to be few reports about this accuracy of the position line. The authors forwarded some research about this problem. When the visual angle subtended by the two (front and rear) beacons is less than a specific value, it is supposed that anyone can not find whether he is on the leading line or not. This threshold value is written by ε. The direction connected the two beacons is x axis, and the normal to it is y. Then the locus of position on which the visual angle is always constant ε is formulated by equation (1). Here, D is the distance between the two beacons, and x is measured from the front beacon. Where x is not so much great, equation (1) is transformed to equation (2) and practically (3). y represents the error of the leading line, and we see this depends on x, x/D, and of course on ε. The authors attempted to measure the value of ε. They observed the leading lights at NAARAIKO. Zigzagging about the leading line, an observer judged whether he is on the line or not, and simultaneously the beacons are photographed by telephoto lens. The observed results are shown on Fig.3. In this figure the white marks represent that the observer judged he is on the line and the black marks represent out of line. From this they concluded that the threshold value ε is about 20". The observer used a binocular, the magnification factor of which is 7. They also concluded that the range of error is represented by the second order equation (3).
社団法人日本航海学会の論文
1976-12-25

導標による位置の線の精度

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