Читать книгу Geography For Dummies - Jerry T. Mitchell - Страница 117

Aerial photography refers to photos of Earth’s surface taken from aircraft. Today many maps produced under government approval at all levels, municipal through federal, are directly derived from aerial photography. Black and white film was a widely used medium historically, but today almost all of this is done with digital cameras.

Infrared photography is also very popular. Infrared energy is contained in the sunlight that strikes Earth and reflects off its surface. You and I can’t see it, but special types of sensors can. Infrared energy readily passes through haze and air pollution, resulting in crisp images even on days when the atmosphere is far from clean.

Because of that very desirable characteristic, infrared photography is widely used in aerial surveys.

The gray tones and colors on an infrared photograph may be very different than those observed on regular black and white or color film. Because of that, the term false color is widely applied to infrared film and photographs. Most bizarrely, vegetation appears red. Indeed, the more lush or healthy the vegetation, which appears downright green to you and me, the redder it appears on an infrared photo. Differences in redness may indicate different kinds of crops or forests, or indicate plant life that is stressed because of disease or drought.