Interaction of visible and NIR with earth surface (soil and water) Flashcards
What are the 4 factors affecting spectral reflectance of soil?
Soil moisture content
Organic content
Structure (surface roughness and texture)
Mineralogical composition e.g. iron oxide content
What does soil moisture play an important role in?
Plant growth and soil health
Hydrological system (water store)
Local weather (evaporation and plant evapotranspiration)
What does moisture/water do to the soil particles?
It ‘coats’ soil particles and fills in airspaces
How does soil moisture impact reflectance/absorption?
Reduces the amount of multiple scattered light
Increases absorption
What is the relationship between moisture content and spectral reflectance?
Inverse relationship
Higher moisture content results in decreased reflectance throughout the visible and near-infrared region
What sensors are typically used to measure soil moisture content?
Microwave sensors
Why are microwave sensors used to measure soil moisture content?
Microwave wavelengths are sensitive to soil moisture
Operate day and night and can see through cloud over
They can penetrate deeper through canopy layers for example
What is the relationship between soil reflectance and particle size?
Increase in soil reflectance with decreasing particle size
What does particle size influence?
The soils…
Susceptibility to wind and water transport
Leaching potential
Water holding capacity
Exchangeable nutrient supply
What does the iron oxide content of soil determine?
Reflectance (higher) in red wavelength
What wavelengths are absorbed when the soil contains iron oxide?
Blue, green and NIR
What happens to the majority of EMR on water?
Absorbed or transmitted
What is the reflectance of clear water like? Low or high?
Low- over the visible, NIR and SWIR
What wavelength bands does water have higher reflectance?
Blue and green
Name three types of reflectance from water (and draw)
Surface Reflectance
Volume Reflectance
Bottom Reflectance
