Aerial Survey

Aerial Survey, study of the Earth's surface using images taken from aircraft or satellites. Aerial survey has become extremely valuable in mapmaking, agriculture, environmental studies, and military operations. Using aerial images, scientists can analyse the effects of soil erosion, observe the growth of forests, manage crops, or help plan the development of cities (see Town Planning). The science of making precise measurements and creating detailed maps from aerial images is called photogrammetry.

Aerial survey involves the use of remote sensing equipment. A remote sensor is any instrument that gathers information about an object or area from a distance. Sophisticated cameras, the most common sensors used in aerial survey, take photographs capable of revealing objects only a few metres or feet in width from altitudes of more than 19 km (12 mi).

Scientists also use digital cameras to record aerial images directly on a computer disc and video cameras to record images on videotape. Unlike conventional photographs, these images can be viewed immediately. Infrared film produces images that show variations in invisible reflected infrared energy, which is particularly useful in gathering information about plant life. Computers are widely used in aerial survey to improve the quality of images and increase the range of information they can provide.

Although aerial photographs were taken from balloons and kites as early as the mid-1800s, aerial survey was not widely employed until World War I, when cameras were mounted in aircraft. Military applications of aerial photography expanded greatly during World War II, when many improvements in aircraft, cameras, and films were introduced. Today, most of the Earth's surface has been recorded by aerial survey.