CHAPTER 5 Atmospheric Influence and Radiometric Correction PRE-PROCESSING A. Dermanis

Atmospheric Influence Ideal situation: - sun and sensor above observed pixel, - flat terrain, - no atmosphere. Ideal situation: - sun and sensor above observed pixel, - flat terrain, - no atmosphere. A. Dermanis

Atmospheric Influence Ideal situation: - sun and sensor above observed pixel, - flat terrain, - no atmosphere. Ideal situation: - sun and sensor above observed pixel, - flat terrain, - no atmosphere. E 0 = incident irradiance E r = reflected irradiance ρ = reflectivity (caracterizes pixel class) L 0 = illuminance (recorded at sensor) A. Dermanis

Atmospheric Influence Ideal situation: - sun and sensor above observed pixel, - flat terrain, - no atmosphere. Ideal situation: - sun and sensor above observed pixel, - flat terrain, - no atmosphere. E 0 = incident irradiance E r = reflected irradiance ρ = reflectivity (caracterizes pixel class) L 0 = illuminance (recorded at sensor) π = solid angle of upper half space where E r is diffused A. Dermanis

Atmospheric Influence Influence of atmosphere: - Incident irradiance E 0 reduced by a factor T 0, - reflected illuminance L 0 reduced by a factor T 0. Influence of atmosphere: - Incident irradiance E 0 reduced by a factor T 0, - reflected illuminance L 0 reduced by a factor T 0. A. Dermanis

Atmospheric Influence Influence of atmosphere: - Incident irradiance E 0 reduced by a factor T 0, - reflected illuminance L 0 reduced by a factor T 0. Influence of atmosphere: - Incident irradiance E 0 reduced by a factor T 0, - reflected illuminance L 0 reduced by a factor T 0. L S = illuminance (recorded at sensor) A. Dermanis

Atmospheric Influence - sun at zenith angle θ over observed pixel, - sensor at zenith angle  over observed pixel. - sun at zenith angle θ over observed pixel, - sensor at zenith angle  over observed pixel. A. Dermanis

Atmospheric Influence - sun at zenith angle θ over observed pixel, - sensor at zenith angle  over observed pixel. - sun at zenith angle θ over observed pixel, - sensor at zenith angle  over observed pixel. E = incident irradiance reduced by a factor T θ > Τ 0 (passing thicker layer) and by a factor cosθ (spread over larger area) L T = illuminance (recorded at sensor) reduced by a factor T  > T 0 A. Dermanis

Atmospheric Influence - sun at zenith angle θ over observed pixel, - sensor at zenith angle  over observed pixel. - sun at zenith angle θ over observed pixel, - sensor at zenith angle  over observed pixel. E = incident irradiance reduced by a factor T θ > Τ 0 (passing thicker layer) and by a factor cosθ (spread over larger area) L T = illuminance (recorded at sensor) reduced by a factor T  > T 0 A. Dermanis

Atmospheric Influence - sun at zenith angle θ over observed pixel, - sensor at zenith angle  over observed pixel. - sun at zenith angle θ over observed pixel, - sensor at zenith angle  over observed pixel. E = incident irradiance reduced by a factor T θ > Τ 0 (passing thicker layer) and by a factor cosθ (spread over larger area) L T = illuminance (recorded at sensor) reduced by a factor T  > T 0 A. Dermanis

Atmospheric Influence Additional incident irradiance E D diffused from atmosphere (origin: sun and other earth pixels) Additional incident irradiance E D diffused from atmosphere (origin: sun and other earth pixels) A. Dermanis

Atmospheric Influence Additional incident irradiance E D diffused from atmosphere (origin: sun and other earth pixels) Additional incident irradiance E D diffused from atmosphere (origin: sun and other earth pixels) E G = incident irradiance L T = illuminance (recorded at sensor) A. Dermanis

Atmospheric Influence Additional illuminance L P diffused from atmosphere (origin: sun and other earth pixels) Additional illuminance L P diffused from atmosphere (origin: sun and other earth pixels) A. Dermanis

Atmospheric Influence Additional illuminance L P diffused from atmosphere (origin: sun and other earth pixels) Additional illuminance L P diffused from atmosphere (origin: sun and other earth pixels) L S = illuminance (recorded at sensor) A. Dermanis

Atmospheric Influence Final situation: E 0 = incident irradiance from sun T θ = atmospheric absorbance on incident irradiance cosθ = reduction factor for pixel inclined to incident radiation E D = irradiance diffused from atmosphere ρ = pixel reflectance π = solid angle of upper half space T φ = atmospheric absorbance on reflected illuminance L P = illuminance diffused from atmosphere Final situation: E 0 = incident irradiance from sun T θ = atmospheric absorbance on incident irradiance cosθ = reduction factor for pixel inclined to incident radiation E D = irradiance diffused from atmosphere ρ = pixel reflectance π = solid angle of upper half space T φ = atmospheric absorbance on reflected illuminance L P = illuminance diffused from atmosphere A. Dermanis

Radiometric Corection illuminance arriving at sensor: A. Dermanis

Radiometric Corection instead of ideal: illuminance arriving at sensor: a = atmospheric condition parameters A. Dermanis

Radiometric Corection instead of ideal: illuminance arriving at sensor: recorded at sensor: k 0, C 0 = nominal sensor parameters instead of ideal: a = atmospheric condition parameters A. Dermanis

Radiometric Corection instead of ideal: illuminance arriving at sensor: recorded at sensor: k 0, C 0 = nominal sensor parameters instead of ideal: Radiometric correction: Recovery of x 0 from x a = atmospheric condition parameters A. Dermanis

Radiometric Correction (a) Sensor Calibration: Computation of k and C (b) Radiometric correction for sensor instability (c) Determination of atmospheric influence parameters (d) Radiometric correction for atmospheric influence A. Dermanis

(a) Sensor Calibration: Computation of k and C (b) Radiometric correction for sensor instability (c) Determination of atmospheric influence parameters θ (flat terrain) = from astronomic ephemeris (replaced by ω for inclined terrain) Radiometric Correction A. Dermanis

(a) Sensor Calibration: Computation of k and C (b) Radiometric correction for sensor instability (c) Determination of atmospheric influence parameters θ (flat terrain) = from astronomic ephemeris (replaced by ω for inclined terrain) φ = from satellite orbit Radiometric Correction A. Dermanis

(a) Sensor Calibration: Computation of k and C (b) Radiometric correction for sensor instability (c) Determination of atmospheric influence parameters θ (flat terrain) = from astronomic ephemeris (replaced by ω for inclined terrain) φ = from satellite orbit T θ, Τ φ = from atmospheric pressure, temperature, humidity Radiometric Correction A. Dermanis

(a) Sensor Calibration: Computation of k and C (b) Radiometric correction for sensor instability (c) Determination of atmospheric influence parameters θ (flat terrain) = from astronomic ephemeris (replaced by ω for inclined terrain) φ = from satellite orbit T θ, Τ φ = from atmospheric pressure, temperature, humidity E D, L P = from atmospheric conditions related to scattering processes (extremely difficult to access!) Radiometric Correction A. Dermanis

(a) Sensor Calibration: Computation of k and C (b) Radiometric correction for sensor instability (c) Determination of atmospheric influence parameters θ (flat terrain) = from astronomic ephemeris (replaced by ω for inclined terrain) φ = from satellite orbit T θ, Τ φ = from atmospheric pressure, temperature, humidity E D, L P = from atmospheric conditions related to scattering processes (extremely difficult to access!) computation of: Radiometric Correction A. Dermanis

unknown ! (a) Sensor Calibration: Computation of k and C (b) Radiometric correction for sensor instability (c) Determination of atmospheric influence parameters θ (flat terrain) = from astronomic ephemeris (replaced by ω for inclined terrain) φ = from satellite orbit T θ, Τ φ = from atmospheric pressure, temperature, humidity E D, L P = from atmospheric conditions related to scattering processes (extremely difficult to access!) computation of: Radiometric Correction A. Dermanis

unknown ! (a) Sensor Calibration: Computation of k and C (b) Radiometric correction for sensor instability (c) Determination of atmospheric influence parameters (d) Radiometric correction for atmospheric influence θ (flat terrain) = from astronomic ephemeris (replaced by ω for inclined terrain) φ = from satellite orbit T θ, Τ φ = from atmospheric pressure, temperature, humidity E D, L P = from atmospheric conditions related to scattering processes (extremely difficult to access!) computation of: Radiometric Correction A. Dermanis