ABSTRACT
Remote sensing may be taken to mean the observation of, or gathering of information about, a target by a device separated from it by some distance. The expression “remote sensing” was coined by geographers at the U.S. Office of Naval Research in the 1960s at about the time that the use of “spy” satellites was beginning to move out of the military sphere and into the civilian sphere. Remote sensing is often regarded as being synonymous with the use of artificial satellites and, in this regard, may call to mind glossy calendars and coffee-table books of images of various parts of the Earth (see, for example, Sheffield [1981, 1983]; Bullard and Dixon-Gough [1985]; and Arthus-Bertrand [2002]) or the satellite images that are commonly shown on television weather forecasts. Although satellites do play an important role in remote sensing, remote sensing activity not only precedes the expression but also dates from long before the launch of the first artificial satellite. There are a number of ways of gathering remotely sensed data that do not involve satellites and that, indeed, have been in use for very much longer than satellites. For example, virtually all of astronomy can be regarded as being built upon the basis of remote sensing data. However, this book is concerned with terrestrial remote sensing. Photogrammetric techniques, using air photos for mapping purposes, were widely used for several decades before satellite images became available. The idea of taking photographs of the surface of the Earth from a platform elevated above the surface of the Earth was originally put into practice by balloonists in the nineteenth century; the earliest known photograph from a balloon was taken of the village of Petit Bicêtre near Paris in 1859. Military reconnaissance aircraft in World War I and, even more so, in World War II helped to substantially develop aerial photographic techniques. This technology was later advanced by the invention and development of radar and thermal-infrared systems.
