Thermal infrared remote sensing
Also called: TRISHNA · Topic: Remote Sensing, GIS and GNSS · NCERT: Beyond NCERT
Meaning
Thermal infrared remote sensing records the heat that surfaces give off, mostly at about 8 to 14 micrometres. It does not depend on reflected sunlight, because warm objects send out this energy themselves. Hotter surfaces send out more of it. This lets scientists map land and sea surface temperature, urban heat islands, water stress in crops and fires. Crops short of water run warmer than well-watered crops, so thermal data can warn of stress before the leaves wilt.
Example
A thermal image of Delhi on a summer afternoon shows dense built-up areas much hotter than nearby parks and the Yamuna floodplain. This is an urban heat island. ISRO and France's CNES are planning the TRISHNA satellite for this kind of thermal mapping.
Don't confuse with
- Near infrared: this is reflected sunlight at about 0.7 to 1.1 micrometre. It shows how green vegetation is, not how hot a surface is.
Related concepts
- Electromagnetic radiation
- Electromagnetic spectrum
- Spectral band
- Near infrared
- Atmospheric absorption and scattering
- Reflectance
- Absorptance
- Spectral signature
- NDVI