04-Multispectral

04-Multispectral - 4/14 ‐ 16/2008 ESM 266: Multispectral...

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Unformatted text preview: 4/14 ‐ 16/2008 ESM 266: Multispectral remote sensing 1 ESM 266: Multispectral ESM 266: Multispectral remote sensing remote sensing 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 2 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 Atmospheric absorption Atmospheric absorption and scattering and scattering emission 3 absorption scattering Relation between frequency and wavelength Relation between frequency and wavelength , so and speed of light, m/s wavelength m (but we often use m or nm) c c c c λυ υ λ λ υ λ μ = = = 4-1 wavelength, m (but we often use m or nm) frequency, Hz (s ) λ μ υ Sun glint and Sun glint and wildfires near wildfires near Carpenteria Carpenteria Bay, Bay, Queensland, Queensland, Australia Australia 4/14 ‐ 16/2008 ESM 266: Multispectral remote sensing 2 Terminology Terminology • Radiant flux Φ , units W • Irradiance (flux density) E, units Wm –2 – (called Exitance M when away from surface) 7 • Radiance L, units Wm –2 sr –1 • Note: All can be functions of wavelength and have units μ m –1 Reflectance Reflectance terminology terminology directional-hemispherical reflectance (or just reflectance) ( ) [dimensionless] cos ( ) M r E θ θ θ = 8-1 r bidirectional reflectance-distribution function ( ) ( , ) ( ; , ) [units sr ] cos ( ) bidirectional re r r r r BRDF L f E θ φ θ θ φ θ θ = r r flectance factor ( ) R( ; , ) ( ; , ) [dimensionless] r r r BRF f θ θ φ π θ θ φ = Relation between flux density and intensity Relation between flux density and intensity If L is isotropic (same for all θ φ ) π π π θ φ θ θ θ φ − = ∫ ∫ /2 ( , )sin cos r r r r r r M L d d 9 π = E L If L is isotropic (same for all θ r , φ r ), then θ r φ r 2 because, if isotropic sin cos 1 2 2 r r r r L M L d d L π π π φ θ θ θ π − = = × × ∫ ∫ Steradian (Solid Angle) Steradian (Solid Angle) • The steradian (sr) is the unit of solid angle – defined as: Ω = A/r 2 Spherical cap Diameter of flat cone area, A Radius, r Ω Sphere Overview of typical system Overview of typical system 11 Format of a multispectral image Format of a multispectral image 255 Brightness value range (typically 8 bit) Associated gray-scale 10 15 17 20 15 16 18 21 1 2 1 5 4 3 2 Columns (j) 1 2 white 21 23 Lines or rows (i) 255 Brightness value range (typically 8 bit) Associated gray-scale 10 15 17 20 15 16 18 21 1 2 1 5 4 3 2 Columns (j) 1 2 white 21 23 Lines or rows (i) 12 127 17 18 20 22 18 20 22 24 3 4 Bands (k) 3 4 re element (pixel) at location 4, Column 4, in Band 1 has a Brightness Value of 24, i.e., BV 4,4,1...
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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 - 4/14 ‐ 16/2008 ESM 266: Multispectral...

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