Lecture 3 Interaction of visible and NIR with surface Flashcards
Spectral Reflectance
The reflectant within a specified wavelength range.
What does spectral reflectance depend on?
- Material Type
- Nature of surface - either specular or diffuse
- Spectral wavelength
- Other Factors
Why study interaction between EMR and vegetation?
Often first surface encountered by RS energy.
Land Surface covered by vegetation
70%
Affect of increased soil moisture on reflectance
Decreased reflectance through visible and IR wavebands
Why is there high NIR reflectance from vegetation?
Spaces between chlorophyll containing moisture reflects NIR
Therefore: What happens with aging leaf reflectance?
Increased due to less chlorophyll so more moisture filling the spaces.
What characteristics would area of dense vegetation have?
Low reflectance in red waveband and high reflectance in NIR
Red Edge
Waveband of EMR which is sensitive to vegetation chlorophyll content
Three major water absorption wavebands
- 1.4 micrometre
- 1.9 micrometre
- 2.7 micrometre
Factors affecting spectral reflectance of vegetation
- Soil Background
- Solar illumination
- Vegetation 3D structure
- Phenology (lifecycle of plants)
Vegetation reflectance Summary
EMR is reflected by chlorophyll in the green and absorbed in the blue and red.
Highly reflected in the NIR due to cellular arrangement and absorbed by moisture in MIR
Which Chlorphyll absorbs blue and red light?
Chlorophyll - a and Chlorophyll - b
Which Chlorphyll absorbs blue and red light?
Chlorophyll - a and Chlorophyll - b
Phenology affecting spectral reflectance of vegetation
During winter reflectance will be lower and lower NDVI due lack of plant growth meaning lower NIR reflection.
In summer during peak growing season NDVI will be higher due to high NIR reflectance from green leaves
