Geographic Information Systems: An Introduction, 3rd Edition

9.5 Aerial Photographs and Photo Interpretation

The concept of aerial photography was patented in 1855 by French writer and photographer Gaspard-Felix Tournachon (1820–1910), who wrote under the pen name of Nadar. In 1856, Tournachon daringly ascended in a balloon from a village near Paris and took the world's first aerial photograph. Since 1909, where airplanes were first employed, aerial photography has become a discipline with its own theory and practice. Because they are taken from above, all objects in aerial photographs appear as viewed from various vertical angles. So aerial photographs almost always require interpretation in order to obtain information for mapping or depicting details as seen from the ground. Of course, almost all photographs used for their information content are interpreted in some way, but the interpretation of aerial photographs for mapping purposes is most common.

The combination of aerial photography and photographic interpretation provides information on relatively large areas without necessitating survey inspection on the ground. Roads, lakes and rivers, buildings, farmland, and forests are clearly visible in aerial photographs (Figure 9.14). Other characteristics, such as various types of vegetation, soil, and geological formations, are more difficult to interpret. Accurate interpretation depends on both experience and verification by ground control. Consequently, photographic interpretation has become a skilled profession. Interpretation is based ...