GEOG 330 Chapter 8-1

GEOG 330 Chapter 8-1 - Thermal Infrared RS GEOG330 Thermal...

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Unformatted text preview: Thermal Infrared RS GEOG330 Thermal Infrared RS Thermal Infrared RS Thermal Infrared RS • Thermal infrared (TIR) energy is emitted from all objects that have a temperature greater than absolute zero • Human eyes cannot detect TIR energy, but there are special detectors that are sensitive to TIR radiation allowing humans to sense a previously invisible world of information as they monitor the thermal characteristics of the landscape. • All the components in the landscape have predictable thermal characteristics based on how they selectively absorb solar short-wavelength energy & radiate long- wavelength TIR energy. Thermal Infrared RS • TIR RS systems acquire images that can be used to: – (1) Determine the type of material based on its thermal emission characteristics – (2) Evaluate significant changes in the thermal characteristics through time • Thus, it is possible to identify stress in plants, thermal pollution in water bodies or atmospheric layers, etc. Thermal Infrared RS • Aerial thermal imagery has not been widely available due to: – (1) The high cost of the thermal sensor; – (2) The cost of mobilizing an aircraft to acquire RS data; – (3) The difficulty of calibrating & correctly interpreting the data Note: Most known applications include medical, electronic, military, & insulation industry Thermal Infrared Radiation Principles • All real world objects above 0 K have random motion called kinetic heat • An object’s kinetic heat is measured in terms of its true kinetic temperature ( T kin ) • When these particles collide they change their energy state & emit EMR, which we refer to as radiant flux ( ! ) • The concentration of the amount of radiant flux exiting an object is called its radiant temperature ( T rad ) Thermal Infrared Radiation Principles • There is a high positive correlation between and object’s T kin and the T rad exiting the object • This relationship is the basis of thermal infrared Remote Sensing T rad T kin Emissivity • Remote measurement of T rad are always lower than the T kin of an object. This is due to a thermal property called emissivity . • The world is not composed of radiating blackbodies. Rather it is composed of selective radiating bodies . • Emissivity ( ! ) is the ratio between the radiant flux exiting a real world selective radiating body ( M r ) and a blackbody at the same temperature ( M b ): " = M r / M b Emissivity • All selective radiating bodies have emissivities ranging from 0 to <1 • A graybody outputs a constant emissivity that is <1 at all wavelengths • Some real world objects & their emissivities : – Distilled water: 0.99 – Stainless steel: 0.16 – Polished aluminum: 0.08 Emissivity • Two objects with the same kinetic temperature might have different radiant temperatures because their emissivities are different....
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This note was uploaded on 01/16/2012 for the course GEOG 330 taught by Professor Marsh during the Fall '07 term at Arizona.

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GEOG 330 Chapter 8-1 - Thermal Infrared RS GEOG330 Thermal...

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