Beyond Spectral and Spatial data: Exploring other domains of information: 1

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Beyond Spectral and Spatial data Exploring other
domains of information 1

• GEOG3010 Remote Sensing
• and Image Processing
• Lewis
• RSU

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Domains of Information

• spectral
• angular
• multi-temporal
• distance-resolved
• spatial

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Domains of Information

• consider physical basis for information

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Spectral - Physical Basis

• Optical
• reflectance varies with wavelength
• spectral reflectance of different cover types /
  properties vary

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Spectral reflectance

• Related to
• how much (projected, illuminated) material seen

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Spectral reflectance

• Related to
• reflectance / absorptance characteristics of
  materials

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Plus multiple scattering where absorptance low
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Leaves

• Absorbtance by leaf pigments, water etc
• Acting in different parts of the spectrum

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Leaves Factors affecting reflectance/transmittanc
e of plant elements

• pigment type/concentration
• e.g. Chlorophyll a,b - absorb visible radiation
• surface features
• hairs, spines, veins, cuticular wax - scattering
  (e.g. specular)
• cell morphology and content
• NIR - high refl. due to scattering at
  refractive index discontinuities
  (nair 0 ncell1.47)
• MIR - water absorption features

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• So attempt to take RS measurement and relate to
• cover type
• different spectral properties
• amount of material (eg vegetation)
• eg leaf
• high NIR, low visible (basis of VIs)

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Interpretation complicated by

• variations in Sun/view angle

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-30
60
0
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e.g. 5m mean tree spacing SZA 0 degrees
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Interpretation complicated by

• projection of objects
• orientation (leaf angle distribution)

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Interpretation complicated by

• projection of objects

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Interpretation complicated

• So relationship between eg VI and canopy
  variables (LAI) depends on cover type
• (different canopy structure)

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Microwave

• Similar spectral concepts
• (frequency c f ?)
• again generally related to amount of material
• but very much driven by
• water content
• size of objects (relative to wavelength)
• orientation
• effect dept. on polarisation

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Summary

• Spectral
• cover type variation
• spectral properties (of leaves, soil etc.)
• projected towards viewer, illuminated
• depends on amount of material
• Vis - e.g. NDVI - quantify amount
• relationships depend on cover type