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Jacob, F, Weiss, M, Olioso, A, French, A (2002). "Assessing the narrowband to broadband conversion to estimate visible, near infrared and shortwave apparent albedo from airborne PoIDER data". AGRONOMIE, 22(6), 537-546.

The airborne PolDER data acquired during the ReSeDA experiment were used to assess the accuracy of the narrowband to broadband conversion, commonly used to express the integrated value of albedo, as a linear combination of waveband estimates. We focused on the estimation of shortwave, visible and near infrared apparent albedos from waveband hemispherical reflectances. The latter were computed using four classical linear BRDF kernel-driven models. The relative discrepancy over the estimates from the four models was about 10%. The narrowband to broadband conversion was performed considering several coefficient sets devoted to recent sensors. The validation against field measurements showed a relative accuracy of shortwave albedo about 9%, whereas it emphasized the quality of visible and near infrared albedos through an indirect procedure. However, the consequences of the theoretical uncertainties, made when calibrating the coefficient sets we used, remain unknown. Similarly, the calibration of coefficient sets devoted to the shortwave albedo estimation from PolDER data showed that it was not possible to discriminate the information provided by the blue, green and red PolDER channels. Indeed, the hemispherical reflectance data set we used was not accurate enough to address experimentally the validity of the spectral interpolation method. Finally, the calibration of coefficients showed that it might be possible to calculate shortwave albedo, with a relative error of 8% using only red and near infrared channels.



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