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Three factors determine canopy reflectance

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3. Directions of illumination and view. ... BRDF: a Goniometer. BRDF 'hot spot' Backscatter direction. Forward scatter direction ... – PowerPoint PPT presentation

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Title: Three factors determine canopy reflectance


1
Three 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 )

2
Three 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 )

3
Bi-directional Reflectance Distribution Function
(BRDF)
Light reflecting off of a surface is rarely
isotropic. Most surfaces exhibit anisotropic
reflectance (reflectance amount varies with
direction).
4
BRDF
Ei(qi,fi)
Lr(qi,fiqr,fr)
BRDF Lr(qi,fiqr,fr)/ Ei(qi,fi)
5
BRDF
sensor
Forward scatter direction
Back scatter direction
6
Canopy BRF is not constant as direction of
illumination changes during day
7
BRDF
Backscatter direction
Forward scatter direction
8
BRDF
Backscatter direction
Forward scatter direction
9
BRDF
Backscatter direction
Forward scatter direction
10
BRDF a Goniometer
11
BRDF
hot spot
Backscatter direction
Forward scatter direction
12
BRDF
13
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