Imagery produced by the sensing of thermal energy emitted or reflected from the objects that are sensed is called thermal imagery. Thermal energy or thermal infrared radiation refers to electromagnetic waves in the 3.5- and 20-μm (micrometer) portion of the spectrum. Most thermal remote sensing applications make use of the 8- to 14-μm range. Earth's surface and atmosphere radiate thermal energy outward owing to heating by solar irradiation and by Earth's internal heat flow. By measuring and recording such emitted radiation in parts of the thermal region of the spectrum, sensors can produce very informative data (as imagery) that provide both distinctive signatures and/or indirect indications of properties of materials, which are sensed, such as vegetation, soil, rock, water, and people. Thermal imagery can be ...