Interaction of EMR with the earth's surface (vegetation) Flashcards
What are the three interactions that the sun’s radiation has on the surface of the earth?
Reflection
Absorption
Transmission
What determines the extent to which radiation is reflected, absorbed, or transmitted?
The spectral and structural properties of the object
What is spectral reflectance?
The reflectance within a specified wavelength (0.3-0.4 micrometers)
What does spectral reflectance depend on?
Material type e.g. vegetation, soil
Nature of the surface e.g smooth or rough
Spectral wavelength
Other factord e.g. time, slope, condition
What is a spectral signature?
Every object on earth has a unique spectral property (reflection, absorption and transmission)
Name 4 reasons to study the interaction between EMR and vegetation?
Often the first surface encountered by the energy used for remote sensing
Vegetation plays a key role in the carbon cycle
Direct interest e.g. disease, biodiversity, forestry
Indirect interest e.g. geologic patterns
What wavelengths (colours) of energy are absorbed by the primary pigments of chlorophyll a and b?
Some blue and red light
Where does the NIR wavelength interact with vegetation?
In the upper half of the leaf in air spaces- high reflectance
How does leaf maturity affect reflectance in the NIR wavelength?
The amount of airspaces increases with the level of maturity which leads to higher reflectance
What is the ‘red edge’?
The sharp change in reflectance between NIR and red wavelengths
What is the ‘red edge’ position relative to?
The amount of chlorophyll in the vegetation
Where will the red edge position be when there is low chlorophyll concentration?
At shorter wavelengths
Where will the red edge position be when there is high chlorophyll concentration?
At longer wavelengths
What determines the reflectance in the SIR (shortwave infrared) wavelength?
Water content
What happens to the reflectance when water content increases?
Decreases- shorter wavelengths
What happens to the absorption when the water content decreases?
Increases- longer wavelengths
What are 4 other factors that affect the spectral reflectance of vegetation?
Soil background i.e. beneath canopy
Solar and sensor geometry
Vegetation 3d structure
Phenology
What is the equation for NDVI, indicating what the paramaters are?
NDVI=
Pnir-Pred/Pnir+Pred
Name two cover types that would have negative NDVI values
Snow, water, clouds
Draw a typical NDVI phenological profile of deciduous vegetation in the northern hemisphere. Annotate the plot with the three key temporal transitions in vegetation phenology.
Onset of greeness, maximum NDVI at peak, End of greenness
Draw the soil line and location of peak biomass on the following pot- red refelectnace and red
Draw the soil line and location of peak biomass on the following pot- red refelectnace and red
