Training Module on Monitoring Vegetation From Space

•  
• 3 - Satellite sensors and vegetation
•  
• 3.1 - Spectral response of different surfaces
•  
• 3.2 - Fundamental factors affecting vegetation reflectance
•  
• 3.3 - The importance of spectral resolution
•  
• 3.4 - Satellite sensors sensitive to vegetation
•  
• 3.5 - RGB images

3.1 - Spectral response of different surfaces

As already mentioned in chapter 2.3 different surfaces have different reflectance spectra. Vegetated and non vegetated surfaces can be recognized by some distinctive broad feature types:

Vegetated surfaces

Beyond 1.3μm, vegetation essentially absorbs or reflects the incident radiation; transmittance is negligible and the dips in the reflectance spectra correspond to absorption at those wavelengths.

Figure 3.1: Reflectance spectrum of green grass.

Non vegetated surfaces

The reflectance curve of non vegetated surfaces (in the figure it is exemplified by sandy soil) has smaller dependence on wavelength. Some of the factors affecting soil reflectance are moisture content, soil texture, surface roughness, presence of iron oxide and organic matter.

Figure 3.2: Reflectance spectrum of sand.