WHILE the matter of using aeroplanes as actual fighting units in warfare is still in dispute, there is no question that they will play a most important part as scouts. In fact, they have actually been used in this capacity by the Italian army in Tripoli. In the very earliest days of aeronautics, this use of the aeroplane was suggested, and pictures were published showing an army .scout m a k i n g sketches from an aeroplane. A later idea has been to use a camera so as to facilitate the work of the scout. It has occur r e d to the artist whose drawing is reproduced herewith, that photography under such circumstances would be rather .difficult, owing to the fact that the machine would have to be b r oug h t within comparatively small elevation above the fortifications that were to be photo-gt a p h ed, and would thus be an easy target for the gunners below. He believes that night photography w o u I d be better; for then the aeroplane could steal into position over the fortifications, and flash its light upon them for a few brief moments . while pictures were taken. The best camera for the purpose w o u 1 d be one adapted to take a kinematographic series of pictures. Out of the set of pic t u res thus taken, there would, he argues, surely be a few which would show the fortifications to good advantage as the .aeroplane passed over them. The brief interval during which the searchlight of the aeroplane would play upon the fortifications might not be sufficient to enable the gun- M ners to take accurate aim upon the aircraft. In order to increase the value of the photographs, it would be well to determine the height of the machine above the fortifications and hence the scale of the pictures. The height above sea level could readily be determined by means of a barometer, but it would not necessarily show the height above the fortifications. However, with a searchlight throwing a conical beam of fixed angle, the spot of light upon a film taken with a camera of known focus, would give an approximate index, from which the height of the machine above the fortifications would be determined. By this means it would be possible to make an accurate survey of the fortifications with a minimum exposure of the aeronauts. Another method of discovering the height of the aeroplane above the fortifications, the artist suggests, is to have two searchlights placed at opposite ends of the machine and mounted to move together in such a way [that their beams would intersect always at a fixed distance below the aeroplane. The height of the aeroplane above the fortifications would then be shown by the size of the intensely illuminated spot produced by the overlapping portions of the beams of light.
This article was originally published with the title "Photographic Scouting at Night" in Scientific American 105, 19, 404 (November 1911)