XXII ISPRS Congress 2012: Technical Commission VII

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Multivolume work

Persistent identifier:: 1663813779

Title:: XXII ISPRS Congress 2012

Sub title:: Melbourne, Australia, 25 August-1 September 2012

Year of publication:: 2013

Place of publication:: Red Hook, NY

Publisher of the original:: Curran Associates, Inc.

Identifier (digital):: 1663813779

Language:: English

Additional Notes:: Kongress-Thema: Imaging a sustainable future

Corporations:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Adapter:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Founder of work:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Other corporate:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Document type:: Multivolume work

Volume

Persistent identifier:: 1663821976

Title:: Technical Commission VII

Scope:: 546 Seiten

Year of publication:: 2013

Place of publication:: Red Hook, NY

Publisher of the original:: Curran Associates, Inc.

Identifier (digital):: 1663821976

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(39,B7)

Language:: English

Additional Notes:: Erscheinungsdatum des Originals ist ermittelt.; Literaturangaben

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Corporations:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Adapter:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Founder of work:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Other corporate:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2019

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: [VII/1: PHYSICAL MODELLING AND SIGNATURES IN REMOTE SENSING]

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: REFLECTANCE CALIBRATION SCHEME FOR AIRBORNE FRAME CAMERA IMAGES U. Beisl

Document type:: Multivolume work

Structure type:: Chapter

— € (D c« «P» p" 4» Q — MMC wA M» International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B7, 2012 XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia 2.2.3 Modelling of Atmospheric Quantities: Now 9, can be parametrized as a function of the observed atmospheric reflectance à, the view zenith angle 6,, the sun zenith angle 6;, the relative azimuth angle ¢ and a set of fixed parameters al...a4. Ô, = 0,(0,0, ---a4,0,,0,,P) (5) Since 6, is a nadir looking quantity there is no explicit azimuth angle dependence. However, the parametrization has to compensate the azimuth angle dependence of the observed atmospheric reflectance à at view zenith angle 0,. The azimuth angle dependence of à is caused by the path radiance Lo which is defined as the total radiance at ground reflectance 0. The total radiance is shown for several ground reflectances in Figure 3 for a visibility of 3 km. For a satellite view the variation of Lo can be modelled with a cos(2*) dependence since it is caused mostly by Rayleigh scattering. For an airborne view at 1 km above ground a modelling with a function cos(1.4*@) is more adequate, since the predominant Mie scattering has a strong backscattering characteristic. Taowns Tup» and s do not have an azimuth angle dependence. 5.60E-04 5.40E-04 y 520E-04 * “ = L(n=8) e IS j A = E 5.00E-04 —%——— paf a un p=0. t v pare / - = ‘cos(20) (p=0) 9 480E-04 / 2 A f — -tos(29) (p-0.2) & 460E-04 SC É en SA di 4 ADE-04 We A 4.20E-04 1 | 0 50. 100150 Az imuth Angle [*] 2.90E-04 2.70E-04 = —L (p=0) N = > 2.50E-04 — | (20.2 > L (p=04) 2308-04 = = 'cos(1.49) (p=0) o S === «pOS(1.49) (p-0.2) 3 9 10E-04 = <COS(I 49) (p=0.4) 1.90E-04 1.70E-04 0 50 100 150 Azimuth Angle ['] Figure 3. Variation of the at-sensor radiance as a function of the view azimuth angle for visibility 3 km and a sensor elevation of 100 km (upper image) and 1 km (lower image). A different ground reflectance p only adds a constant radiance offset. The variation can be modelled with a cosine function. The atmospheric reflectance 6, is the scaling factor for the other atmospheric quantities Ly, Tgown, Typ, and s. They are calculated as a function of the observed atmospheric reflectance 3, the view zenith angle 6,, the sun zenith angle 6;, the ground level H, the flight altitude over ground h and a set of fixed parameters (b;...b;, c,...cs, d;...d,, e;...eg). The parameters for the quantities in eqns (5)-(9) can be obtained using a multilinear regression from a sufficient number of model runs with all combinations of the input variables. L, = L,(b--5,,0,,0,,0,0,,h,H) (6) T mm T. miei c6, OS fi EDS (7) I, =T,(d\-d;.6,,0,) (8) $zs(e,--:e,, 6, ,h, H) (9) 2.2.4 Broadband Sensors: The above calculation is strictly valid only for a single wavelength and the outputs being spectral densities. The evaluation of eqn (2) gives the contribution to the reflectance at this wavelength. For a broadband sensor the contributions of a spectral density x have to be integrated over the spectral response curve of the sensor using eqn (10) to give the band-averaged quantity. [x(A)R()aA ce 10 de Eire a This would require to parametrize the quantities in eqns (5)-(9) for each wavelength separately which is not practical. So the parametrization is done for the band averaged quantities in eqns (5)-(9) and the reflectance is then calculated from the band- averaged quantities. (Richter, 2000) has found that the errors in the VISNIR range (400-1000 nm) are below 2% and therefore below the calibration accuracy. In the special case of a narrowband sensor with spectral sensitivities away from the gaseous absorption bands (like e.g. the ADS) the atmospheric quantities Lo, Tgown, Tup, and s change moderately with wavelength. Then the radiative transfer calculations can be made by using the effective bandwidth of the sensor and simply averaging the spectral quantities over the effective bandwidth without using the spectral response function as a weight. 2.2.5 Reflectance Calibration for Images: Eqns (2) and (5)- (9) allow a fast image calibration to ground reflectance without any iteration. Since multiple scattering is a second order process p can be assumed constant and an average value of 0.15 for a midlatitude landscape is used. 2.3 Bidirectional Reflectance 2.3.1 Sampling and Model Inversion: As mentioned in (Beisl et al, 2004) the bidirectional reflectance process is influenced mainly by microscopic shadow casting and volume scattering processes with unknown influencing parameters. So the correction process also requires a model inversion. As suggested by the viewing geometry shown in sec. 2.1 the sampling has to be done in image columns for the line scan

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