CHAPTER 2 Basic Definitions And Laws Of Electromagnetic Radiation FUNDAMENTALS A. Dermanis

Sensors collect electromagnetic energy ΔQ emitted from a surface area ΔΑ (pixel), during a time interval Δt, arriving at the sensor aperture with a solid angle ΔΩ ΔΑΔΑ ΔΩ P A. Dermanis

Sensors collect electromagnetic energy ΔQ emitted from a surface area ΔΑ (pixel), during a time interval Δt, arriving at the sensor aperture with a solid angle ΔΩ ΔΑΔΑ ΔΩ Το characterize the “intensity” of electromagnetic radiation we must get rid of ΔΑ, Δt and ΔΩ ! P A. Dermanis

Sensors collect electromagnetic energy ΔQ emitted from a surface area ΔΑ (pixel), during a time interval Δt, arriving at the sensor aperture with a solid angle ΔΩ ΔΑΔΑ ΔΩ Το characterize the “intensity” of electromagnetic radiation we must get rid of ΔΑ, Δt and ΔΩ ! Basic definitions ( Q = energy) P A. Dermanis

Sensors collect electromagnetic energy ΔQ emitted from a surface area ΔΑ (pixel), during a time interval Δt, arriving at the sensor aperture with a solid angle ΔΩ ΔΑΔΑ ΔΩ Το characterize the “intensity” of electromagnetic radiation we must get rid of ΔΑ, Δt and ΔΩ ! Basic definitions ( Q = energy) radiant flux Φ(t) : P (power !) A. Dermanis

Sensors collect electromagnetic energy ΔQ emitted from a surface area ΔΑ (pixel), during a time interval Δt, arriving at the sensor aperture with a solid angle ΔΩ ΔΑΔΑ ΔΩ Το characterize the “intensity” of electromagnetic radiation we must get rid of ΔΑ, Δt and ΔΩ ! Basic definitions ( Q = energy) radiant flux Φ(t) : radiant exitance M(t,P) : P (emitted) (power !) A. Dermanis

Sensors collect electromagnetic energy ΔQ emitted from a surface area ΔΑ (pixel), during a time interval Δt, arriving at the sensor aperture with a solid angle ΔΩ ΔΑΔΑ ΔΩ Το characterize the “intensity” of electromagnetic radiation we must get rid of ΔΑ, Δt and ΔΩ ! Basic definitions ( Q = energy) radiant flux Φ(t) : radiant exitance M(t,P) : P irradiance E(t,P) : (emitted) (incident) (power !) A. Dermanis

Sensors collect electromagnetic energy ΔQ emitted from a surface area ΔΑ (pixel), during a time interval Δt, arriving at the sensor aperture with a solid angle ΔΩ ΔΑΔΑ ΔΩ Το characterize the “intensity” of electromagnetic radiation we must get rid of ΔΑ, Δt and ΔΩ ! Basic definitions ( Q = energy) radiant flux Φ(t) : radiant exitance M(t,P) : P irradiance E(t,P) : illuminance L : (emitted) (incident) ( π = half upper space) (power !) A. Dermanis

Electromagnetic signals x(t) consist of sines and cosines with varying periods T, or angular frequencies ω = 2π/Τ, or wavelengths λ = cT ( c = light velocity) A. Dermanis

Electromagnetic signals x(t) consist of sines and cosines with varying periods T, or angular frequencies ω = 2π/Τ, or wavelengths λ = cT ( c = light velocity) Fourier analysis: A. Dermanis

S (ω) = power spectral density function signal power: A. Dermanis

S (ω) = power spectral density function signal power: radiant flux (power): exitance (with ω  λ = cT = 2πc/ω) : A. Dermanis

= spectral exitance S (ω) = power spectral density function signal power: radiant flux (power): exitance (with ω  λ = cT = 2πc/ω) : A. Dermanis

Sensors respond to exitance only within a spectral band λ 1  λ  λ 2 : Ideal sensor: A. Dermanis

Sensors respond to exitance only within a spectral band λ 1  λ  λ 2 : Actual sensor: w(λ) = sensor sensitivity response function Ideal sensor: A. Dermanis

Sensors respond to exitance only within a spectral band λ 1  λ  λ 2 : Actual sensor: w(λ) = sensor sensitivity response function Ideal sensor: response functions for the 4 sensors of the Landsat satellite Multispectral Scanner A. Dermanis

cm mkmA A μ γ λ Χ UV IR VISIBLE MICROWAVES RADAR RADIOAUDIOAC The Electromgnetic Spectrum Red  IR (Infrared)UV (Ultraviolet)  Violet A. Dermanis

Spectral Bands ofLandsat Satellite - Thematic Mapper (T1, T2, T3, T4, T5) and SPOT4 Satellite – HRVIR (S1, S2, S3, S4) Spectral Bands ofLandsat Satellite - Thematic Mapper (T1, T2, T3, T4, T5) and SPOT4 Satellite – HRVIR (S1, S2, S3, S4) 1. water 2. vegetation 3. bare soil 4. snow A. Dermanis

Laws of Electromgnetic Radiation black body : an idealized body absorbing all wavelengths of incident radiation or emitting radiation at all wavelengths Physical approximation = sun! T = temperature black body : an idealized body absorbing all wavelengths of incident radiation or emitting radiation at all wavelengths Physical approximation = sun! T = temperature A. Dermanis

Laws of Electromgnetic Radiation Law of Plank: (spectral exitance of black body) black body : an idealized body absorbing all wavelengths of incident radiation or emitting radiation at all wavelengths Physical approximation = sun! T = temperature black body : an idealized body absorbing all wavelengths of incident radiation or emitting radiation at all wavelengths Physical approximation = sun! T = temperature A. Dermanis

Laws of Electromgnetic Radiation Law of Plank: (spectral exitance of black body) Law of Stefan-Bolzman: (total spectral exitance) black body : an idealized body absorbing all wavelengths of incident radiation or emitting radiation at all wavelengths Physical approximation = sun! T = temperature black body : an idealized body absorbing all wavelengths of incident radiation or emitting radiation at all wavelengths Physical approximation = sun! T = temperature A. Dermanis

Laws of Electromgnetic Radiation Law of Plank: (spectral exitance of black body) Law of Stefan-Bolzman: (total spectral exitance) Law of Wien: ( λ of maximal spectral exitance) black body : an idealized body absorbing all wavelengths of incident radiation or emitting radiation at all wavelengths Physical approximation = sun! T = temperature black body : an idealized body absorbing all wavelengths of incident radiation or emitting radiation at all wavelengths Physical approximation = sun! T = temperature A. Dermanis

The Solar Electromgnetic Radiation solar irradiance below atmosphere atmospheric absorption A. Dermanis