Reflectance
Topic: Remote Sensing, GIS and GNSS · NCERT: Class 11, Ch 6 "Introduction to Remote Sensing"
Meaning
Reflectance is the share of the energy falling on a surface that the surface reflects back. Every surface reflects different amounts at different wavelengths. Soil, vegetation, water and buildings each have their own reflectance pattern, which is called a spectral signature. Sensors use these differences to tell one surface from another. Without reflectance differences, a satellite image would be one flat shade.
Example
At Sambhar Lake in Rajasthan, shallow salt-covered and dry surfaces reflect much of the light, so they look light-toned in images. Deeper fresh water absorbs red and near infrared and reflects very little, so it looks dark.
Don't confuse with
- Absorptance: this is the share of incoming energy a surface absorbs instead of sending back. High absorptance means low reflectance.
Related concepts
- Electromagnetic radiation
- Electromagnetic spectrum
- Spectral band
- Near infrared
- Atmospheric absorption and scattering
- Thermal infrared remote sensing
- Absorptance
- Spectral signature
- NDVI