The original purpose of military aviation was reconnaissance. Initially, the pilot or observer simply noted down what he could see, and wrote up a report when he landed. During early 1915, the British followed the French in starting to use cameras to photograph the German front. In the earliest scout planes, an observer leant over the side holding a camera and took a photo, then had to change the glass-plate negative, then leaned over the side and took another photo. It was a cumbersome process, but the quality of the imagery was high.
From the Battle of Neuve Chapelle in March 1915, aerial photos were put together in a ‘mosaic’, like a photographic map. For the rest of the war, photo-maps of the German trenches were always produced before an attack. Photo-interpreters became skilled in identifying where the barbed-wire was thickest, where machine-guns were positioned, and where behind the lines the enemy’s artillery was located.
Cameras grew more sophisticated as the war progressed, and were fixed to the side of the aircraft. They were triggered by a remote control operated by the pilot or observer. By the end of the war, flexible roll-film had replaced glass-plates. Lenses improved in quality, and by 1918 huge lenses of up to 20-inch focal length were able to record good, readable images from 20,000 feet.
Tens of thousands of photo-maps were produced during the war. During the Battle of the Somme, some 19,000 aerial photos of German positions were taken, and 430,000 prints were made. In the course of 1918, over 10 million aerial photographs were delivered to the armies in Belgium and France.
This article appeared in issue 52 of Military History Monthly.