Title: Three factors determine canopy reflectance
1Three factors determine canopy reflectance
- 1. Spectral scattering/absorbing properties of
canopy components. (leaves, stems, flowers,
fruit, soil, etc.) - 2. Canopy architecture. (above-ground biomass
leaf area index arrangement of foliage in
x,y,z,q,f space for example, are all leaves
vertical and located in one layer or perhaps
they are arranged in space like the area on a
sphere etc.) - 3. Directions of illumination and view. (Is the
sun the only significant source or does
aerosol- or Rayleigh-scattered light provide
hemispherical illumination is direction of view
toward the hot spot or nadir or )
2Three factors determine canopy reflectance
- 3. Directions of illumination and view. (Is the
sun the only significant source or does
aerosol- or Rayleigh-scattered light provide
hemispherical illumination is direction of view
toward the hot spot or nadir or )
3Bi-directional Reflectance Distribution Function
(BRDF)
Light reflecting off of a surface is rarely
isotropic. Most surfaces exhibit anisotropic
reflectance (reflectance amount varies with
direction).
4BRDF
Ei(qi,fi)
Lr(qi,fiqr,fr)
BRDF Lr(qi,fiqr,fr)/ Ei(qi,fi)
5BRDF
sensor
Forward scatter direction
Back scatter direction
6Canopy BRF is not constant as direction of
illumination changes during day
7BRDF
Backscatter direction
Forward scatter direction
8BRDF
Backscatter direction
Forward scatter direction
9BRDF
Backscatter direction
Forward scatter direction
10BRDF a Goniometer
11BRDF
hot spot
Backscatter direction
Forward scatter direction
12BRDF
13(No Transcript)