1. Light and Radiation

Spectral analysis: Colour glass filters    (4/4)

Processing of TM bands for false colour images

Bands 2 (green-yellow), 3 (red) and 4 (near infrared) of the TM image of central Italy and the processes done to obtain a false colour image. Band 2 is interpreted as B channel, band 3 as G channel and band 4 as R channel of an RGB image. Vegetation reflects sunlight strongly in the near infrared, and therefore shows up very bright in band 4. Hence, vegetation is displayed in red colour in the RGB image, which results in a method for classifying vegetation.

 

 

Because of the colours given to the used bands in the RGB composite, this type of images is often denoted as NRG imagery (near IR as R channel, red as G channel, green as B channel).

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NRG image central Italy
Bands 2 (green-yellow), 3 (red) and 4 (near infrared) of the TM image of central Italy and the processes done to obtain a false colour image.

Exercise: Reflectances

Compare the black-and-white images of bands 1 to 4 with the false colour image.

  1. Evaluate the reflectances of vegetated and non-vegetated land surfaces and of the seawater based on their brightness.
  2. Have a look at the table of TM bands on the preceding page. Can you confirm the descriptions unter column characteristics?
  3. Investigate your findings further by comparing with information in related SEOS pages on

No answers are suggested for this task.