Airships past and present, together with chapters on the use of balloons in connection with meteorology, photography and the carrier pigeon . - ^ fv - /&V ?? I r&t :?^W „i ? 1 Fig. 217.—The village of Rudow, as shown onthe ordnance map. .N I i I. 342 AIRSHIPS PAST AND PRESENT. original was taken on a whole plate, but in order to save space,it has here been somewhat reduced. From the middle of thenetwork a line is drawn to P, making an angle of 67° 30 withXX, and on this in the foreground a distance from the middlepoint equal to 6,300 ft. is measured off. The point P is thusobtained, and a perp
Airships past and present, together with chapters on the use of balloons in connection with meteorology, photography and the carrier pigeon . - ^ fv - /&V ?? I r&t :?^W „i ? 1 Fig. 217.—The village of Rudow, as shown onthe ordnance map. .N I i I. 342 AIRSHIPS PAST AND PRESENT. original was taken on a whole plate, but in order to save space,it has here been somewhat reduced. From the middle of thenetwork a line is drawn to P, making an angle of 67° 30 withXX, and on this in the foreground a distance from the middlepoint equal to 6,300 ft. is measured off. The point P is thusobtained, and a perpendicular is drawn through P, cutting theline YY at H. If the central point is called 0, the triangle OPHcorresponds to that formed by the lens, the point vertically belowthe balloon, and the object. The angle PHO is 67° 30, and HPis 2,600 ft. A line through H is drawn parallel to OP, and this cutsthe line XX in the vanishing point, V. On the line YYarbitrary lengths are laid off, each measuring, say, 500 yards. Ifthe points on YY are then joined to V, the horizontal distancesbetween these lines will be everywhere equal. It will be noticedthat these distances appear to become less, and at the vanishing-point they absolutely disappear. S
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Keywords: ., bookcentury1900, bookdecade1900, bookpubl, booksubjectaeronautics
