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Infrared Remote Sensing

What is Infrared?

Infrared is Electromagnetic Radiation (EMR) with wavelengths longer than those of visible light and shorter than radio waves. These range from about 700 nanometers (nm) to 1 millimeter (mm).

Infrared remote sensing makes use of infrared sensors to detect infrared radiation(IR) emitted from the Earth’s surface. The mid-wave infrared (MWIR) and long-wave infrared (LWIR) are within the thermal infrared region.

These radiations are emitted from warm objects such as the Earth’s surface. They are used in satellite Remote Sensing for measurements of the earth’s land and sea surface temperature. Thermal infrared remote sensing is also often used for detection of forest fires.

Infrared Radiation uses

It is used in a variety of applications;

  • Communications and networking
  • Wired and wireless operations
  • Remote controls use near-infrared light, transmitted with light-emitting diodes (LEDs)
  • Fiber optic cables to transmit data

Infrared Waves

The Infrared waves are longer than those of visible light, but shorter than those of radio waves. Wavelengths longer than visible light are called infrared rays. Molecules are heated by infrared waves.

WavesWavelength- λ (m)Frequency- v (hertz[Hz])E (electron-volt [eV])
Infrared0.7510-6 410141.65

Characteristics of Infrared waves:

  • Invisible electromagnetic waves that are detected as heat
  • Used in heat lamps
  • Can be detected with special devices such as night goggles
  • Higher energy than microwaves but lower than visible light

Infrared Spectrum

Wave DivisionWavelength (μm)Frequency (THz)Characteristics
Near infra-red0.75-1.4214-400Atmospheric water absorption
Short wave infra-red1.4-3100-214Atmospheric water absorption increases significantly at 1.45 um. 1.53 to 1.56 um is used in long distance communication
Medium wave infra-red3-837-100Heat seeking missiles are designed to work in this spectrum
Long wave infra-red8-1420-37Thermal imaging region
[μm:represent as Microns, also known as micrometer. THz:- Terahertz, a unit of frequency, defined as one trillion (1012) cycles per second or 1012 hertz.]

Infrared Radiation Index

Perform Infrared Radiation (IR) Index; Sundarbans Landsat TM Satellite image, using Erdas Imagine Software.

At first open Indices window; on the main menu, select Raster > drop-down Unsupervised > click Indices.

1. Now indices window is appeared, select Input file (ex.- sundarbans), then go to destination folder and enter Output file name.

2. Choose your satellite data Sensor (ex.- Landsat 4 TM).

3. In the Index section, choose your query:- IIInfrared Index.

4. Finally click OK button.

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