04-Multispectral

04-Multispectral - ESM 266: Multispectral remote sensing...

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ESM 266: Multispectral remote  ESM 266: Multispectral remote  sensing sensing
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2 Radiation and remote sensing Radiation and remote sensing For example, if energy being sensed comes from the Sun, it: is radiated by atomic particles at the source (the Sun) propagates through the vacuum of space at the speed of light interacts with Earth's atmosphere interacts with Earth's surface interacts with Earth's atmosphere once again, and finally reaches our sensing system where it interacts with various optical systems, filters, emulsions, or detectors
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3 Atmospheric absorption Atmospheric absorption and scattering and scattering absorption scattering emission
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4 Relation between frequency and wavelength Relation between frequency and wavelength -1 , so   and   speed of light, m/ s  wavelength, m (but we often use  m or nm)  frequency, Hz (s ) c c c c λυ υ λ μ = = =
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Sun glint and  Sun glint and  wildfires near  wildfires near  Carpenteria Bay,  Carpenteria Bay,  Queensland,  Queensland,  Australia Australia
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7 Terminology Terminology Radiant flux Φ, units W Irradiance (flux density) E, units Wm –2 (called Exitance M when away from surface) Radiance L, units Wm –2 sr –1 Note: All can be functions of wavelength and have units μm –1
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8 Reflectance terminology Reflectance terminology -1 r directional-hemispherical reflectance (or just reflectance) ( )  [dimensionless] cos ( ) bidirectional reflectance-distribution function ( ) ( , ) ( ; , )  [units sr ] cos ( ) bidirectional re r r r r M r E BRDF L f E θ θ φ θ θ φ = = r r flectance factor ( ) R( ; , ) ( ; , ) [dimensionless] r r r BRF f π =
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9 Relation between flux density and intensity Relation between flux density and intensity π = E L If  L  is isotropic  (same for all  θ r , φ r ),  then  r φ r π π θ φ θ θ φ - = / 2 0 ( , )sin cos r r r r r r M L d d 2 0 because, if isotropic sin cos 1 2 2 r r r r L M L d d L - = =
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Steradian (Solid Angle) Steradian (Solid Angle) The steradian (sr) is the unit of solid angle defined as: = A/r 2 Diameter of flat cone Spherical cap area, A Radius, r Sphere
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11 Overview of typical system Overview of typical system
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12 Format of a multispectral image Format of a multispectral image 0 127 255 Brightness value range (typically 8 bit) Associated gray-scale 10 15 17 20 15 16 18 21 17 18 20 22 18 22 24 1 2 3 4 1 5 4 3 2 Columns (j) Bands (k) 1 2 3 4 X axis Picture element (pixel) at location Line 4, Column 4, in Band 1 has a Brightness Value of 24, i.e., BV 4,4,1 = 24. black gray white 21 23 25 Lines or rows (i)
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13 Detector configurations: breaking up the  Detector configurations: breaking up the  spectrum spectrum
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14 Characteristics of several sensors Characteristics of several sensors
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Spatial, spectral characteristics of some multispectral sensors Spatial, spectral characteristics of some multispectral sensors 1.0 10 0.4 1.5 15 3 5 8 12 0.5 0.8
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This note was uploaded on 08/06/2008 for the course ESM 266 taught by Professor Dozier during the Spring '08 term at UCSB.

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04-Multispectral - ESM 266: Multispectral remote sensing...

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