Remote sensing deals with the art and science of observing and measuring items on the Earth’s surface from a distance. By this definition remote sensing encompasses the field of aerial photography. The term, “remote sensing,” was first introduced in 1960 by Evelyn L. Pruitt of the U.S. Office of Naval Research. However, the first aerial photograph was taken in 1858, 102 years before the term “remote sensing” came into existence. Long before satellites and microcomputers started dominating the field of remote sensing, people were taking pictures of the Earth’s surface from afar. Taking these pictures was not an easy task and people risked their lives to bring about the development of the field. To appreciate what was involved, a brief history of aerial photography is provided in this unit.
Once a technique was established for taking pictures, an adequate aerial platform was needed for taking aerial photographs. The only platforms available at the time were balloons and kites. In 1858, Gaspard Felix Tournachon (later known as “Nadar”) captured the first recorded aerial photograph from a balloon tethered over the Bievre Valley. However, the results of his initial work were apparently destroyed. On the other hand his early efforts were preserved in a caricature (Figure 3) prepared by Honoré Daunier for the May 25, 1862 issue of Le Boulevard. Nadar continued his various endeavors to improve and promote aerial photography. In 1859, he contacted the French Military with respect to taking “military photos” for the French Army’s campaign in Italy and preparing maps from aerial photographs. In 1868 he ascended several hundred feet in a tethered balloon to take oblique photographs of Paris (Figure 5).
On October 13, 1860, James Wallace Black, accompanied by Professor Sam King, ascended to an altitude of 1200 feet in King’s balloon and photographed portions of the city of Boston (Figure 4). A cable held the balloon in place. Black, the photographer, made eight exposures of which only one resulted in a reasonable picture. This is the oldest conserved aerial photograph. He worked under difficult conditions with the balloon, which although tethered, was constantly moving. Combined with the slow speed of the photographic materials being used it was hard to get a good exposure without movement occurring. He also used wet plates and had to prepare them in the balloon before each exposure. After descending to take on more supplies, King and Black went up again with the idea of not only covering Boston but also recording the surrounding countryside. However, they encountered other problems. As they rose, the hydrogen expanded causing the neck of the balloon to open more. This resulted in the gas flowing down on their equipment and turning the plates black and useless. In addition, the balloon took off and they landed in some high bushes in Marshfield, Massachusetts, about thirty miles away from their beginning point. It was obvious that the balloon possessed problems in being an aerial platform.
M.Arthur Batut (Figure 6a) took the first aerial photographs using a kite. It was taken over Labruguiere, France in the late 1880s. The camera, attached directly to the kite, had an altimeter that encoded the exposure altitude on the film allowing scaling of the image Figure 6c). A slow burning fuse, responding to a rubber band-driven device, actuated the shutter within a few minutes after the kite was launched. A small flag dropped once the shutter was released to indicate that it was time to bring down the kite. Batut took his first aerial photograph in May 1888. However, due to the shutter speed being too slow, the image was not very clear (Figure 6b). After some modification to the thickness of the rubber band a good shutter speed was obtained.
In 1906, George R. Lawrence took oblique aerial pictures of San Francisco after the earthquake and fires (Figure 8). Using between nine and seventeen large kites to lift a huge camera (49 pounds) he took some of the largest exposures (about 48 x 122 cm or 18 x 48 in.) ever obtained from an aerial platform. His camera was designed so that the film plate curved in back and the lens fitted low on the front, providing panorama images (Figure 7a). The camera was lifted to a height of approximately 2,000 feet and an electric wire controlled the shutter to produce a negative. Lawrence designed his own large-format cameras and specialized in aerial views. He used ladders or high towers to photograph from above. In 1901 he shot aerial photographs from a cage attached to a balloon. One time, at more than 200 feet above Chicago, the cage tore from the balloon, and Lawrence and his camera fell to the ground. Fortunately telephone and telegraph wires broke his fall; he landed unharmed. He continued to use balloons until he developed his method for taking aerial views with cameras suspended from unmanned kites, a safer platform from his perspective. He developed a means of flying Conyne kites in trains and keeping the camera steady under varying wind conditions. This system he named the ‘Captive Airship’ (Figure 7b).
In 1903, Julius Neubranner, photography enthusiast, designed and patented a breast-mounted aerial camera for carrier pigeons (Figure 10). Weighing only 70 grams the camera took automatic exposures at 30-second intervals along the flight line flown by a pigeon. Although faster than balloons they were not always reliable in following their flight paths. The birds were introduced at the 1909 Dresden International Photographic Exhibition. Picture postcards of aerial photographs taken over the exhibition were very popular. They were used at other fairs and for military surveillance. Two sample pictures are provided below (Figure 9a-b). One can see in the one picture the tips of the bird’s wings as it flew across a palace.
In order for the pigeons to carry such small cameras and take several pictures in one flight, a new type film and a smaller camera system were needed. In the 1870s, George Eastman, born in the rural community of Waterville in upstate New York, was an accountant in Rochester. After working five years in a bank, he became bored with the monotony of the job. In 1878, he decided to take a vacation to the island of Santo Domingo and re-evaluate his life. To record his trip he acquired a wet-plate camera outfit. However, he found the camera and assorted darkroom equipment to be cumbersome and bulky. He would need a small wagon to carry all of the materials and equipment, an arrangement not suited for taking pictures on one’s vacation. He soon forgot about the trip to Santo Domingo and became intrigued with the idea of developing a better film and camera system.
In 1879, Eastman discovered the formula for making a successful gelatin emulsion covered dry-plate and built a machine for coating dry plates with the emulsion. These developments led to the invention of rolled paper film. The resulting prints were sharp, clear and free from paper grain distortion. In 1889, his company, Kodak, introduced flexible celluloid film and the popularity of photography soared. He now needed a camera to take advantage of the new film. In 1900, outfitted with a simple lens and the ability to handle rolled film, the one-dollar Kodak box camera, called the Brownie, made Kodak and photography almost synonymous. Eastman had not only revolutionized the field of photography but set the stage for new developments in the field of aerial photography. His work was shortly followed in 1903 by the Wright Brothers’ first successful flight of a heavier-than-air aircraft. Another type of aerial platform was available.
World War I
At the beginning of World War I the military on both sides of the conflict saw the value of using the airplane for reconnaissance work but did not fully appreciate the potential of aerial photography. Initially, aerial observers, flying in two-seater airplanes with pilots, did aerial reconnaissance by making sketch maps and verbally conveying conditions on the ground. They reported on enemy positions, supplies, and movements; however, some observers tended to exaggerate or misinterpret conditions. In some cases, their observations were based on looking at the wrong army. From above, identifying one soldier from another was not easy. One time a German observer indicated that an English unit was running around in great disarray and appeared to be in a state of panic. The English were playing soccer.
Some English observers started using cameras to record enemy positions and found aerial photography easier and more accurate than sketching and observing (Figure 12). The aerial observer became the aerial photographer (Figure 11). Soon all of the nations involved in the conflict were using aerial photography. The maps used by both sides in the Battle of Neuve-Chappelle in 1915 were produced from aerial photographs. By the end of the war the Germans and the British were recording the entire front at least twice a day. Both countries possess up-to-date records of their enemy’s trench construction (Figure 13). England estimated that its reconnaissance planes took one-half million photographs during the war, and Germany calculated that if all of its aerial photographs were arranged side by side, they would cover the country six times. The war brought major improvements in the quality of cameras; photographs taken at 15,000 feet (4,572 meters) could be blown up to show footprints in the mud.
In addition to Fairchild’s and Goddard’s accomplishments between World War I and World War II,several other significant developments occurred within the field of remote sensing during this period. These developments are outlined below.
- 1920’s – First books on aerial photo interpretation were published. Reeves’ Aerial Photographs, Characteristics and Military Applications was published in 1927 followed by Winchester’s and Wills’ Aerial Photography, a Comprehensive Survey of Its Practice and Development and Pendleton’s Map Complication from Aerial Photographs in 1928. McKinley’s Applied Aerial Photography became available in 1929.
- 1924 – Mannes and Godousky patent their research on developing multi-layer color film. Their work led to Kodak producing Kodachrome in 1935. Among the first users of color film for aerial photography was Goddard in 1937. Color film was not used much for aerial photography until after World War II. Film speeds were too slow; camera lenses designed to correct for color were not readily available; atmospheric haze problems existed; and film processing was not consistent.
- 1920’s-30’s – Interest in the peaceful uses of aerial photography increased during this period. Aerial photography had been taken for more than two-thirds of continental United States, most of which was taken in the later half of the thirties. Three federal agencies, namely the Soil Conservation Service, Agricultural Adjustment Administration, and the Forest Service, accounted for most of the work in aerial photography. Other agencies involved in aerial photography work
To be continue……
HISTORY OF REMOTE SENSING, AERIAL PHOTOGRAPHY (Part 2. Period World War II-1960)
Source: Professor Paul R. Baumann
Department of Geography
State University of New York