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Thermal Remote Sensing

 
  In this page we concentrate on the use of thermal spectral data generated by earth observation satellites, such as the current NOAA AVHRR and Thematic Mapper. The aerospace thermal imagery contains spatial information about the surface and near surface temperatures of the earth, which influences the process of the land phase of the hydrologic cycle. This source of thematic spatial information can be merged with other data, field data and other thematic derived from other bands of satellite images, using GIS operations or analysis.

Infra-red sensing exploits the fact that everything above the absolute zero (0ēK or -273ēC) emits radiation in the infra-red range of electromagnetic spectrum, in quantities and at wavelength that depend on nature of the surface (its emissivity) and on its temperature. It is well known that the infra-red range exhibits strong thermal effects. For this reason, the range is called as thermal range. This radiation can be detected by a radiometer or an infra-red scanner. The following table show two themal bands from NOAA-AVHRR which their spatial resolution are 1.1 kilometres and one thermal band from Thematic Mapper which spatial which its spatial resolution is 120 metres.

Band

NOAA AVHRR

Landsat 5 TM

Middle Infra-red

Band 3: 3,55-3,93 m m

Band 7: 2,08-2,35 m m

Thermal Infra-red

Band 4: 10,3-11,3 m m

Band 6: 10,40-12,5 m m

 

Band 5: 11,5-12,5 m m

 

This imagery is called thermal imagery and is caused by the density of imagery depending on the surface temperatures. The highest temperature area appear white, and the lowest temperature areas appear black on it. Consequently, to change actual surface temperature from image density must be measures at least at one point on the ground while scanner is passing over the point. Practically, it is difficult to be done in the field related to space and time, and this environmental variable always changes.

What can we do to discover a more realistic method of ground truth data acqusition in order to acquire actual surface temperatures derived from thermal band of satellite images?

We need monthly average surface temperatures used as one of evironmental variables!

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This page is continued, see the Assessment of Ground Surface Temperatures for Thermal Infra-red Usages

 
 
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Last revised: July 06, 2000