Transcript Document

Specular vs. Diffuse Reflectance
Bidirectional Reflectance Distribution
Function
• BRDF = ratio of
reflected radiance to
the incident irradiance
on a flat surface.
θr
θi
Φi
• Varies with:
– Wavelength
– Angle of incident
irradiance
– Azimuth of reflection
Φr
BRDF
• Light reflected in different geometries depending
on wavelength, object properties and illumination
angles.
Measurement of BRDF
• Measured in the field
over different surface
types using a
goniometer.
Example of measured BRDFs
• Plots of BRDFs
(normalized to nadir
BRDF) of grass
surface
Spectral signatures
Snow vs. cloud spectral reflectance
Snow spectral reflectance and absorption
coefficient of ice
Reflectance of green and dry vegetation
Reflectance of soil
“Broadband” (shortwave) albedo
“Broadband” (longwave) emissivity