24 October 2012 A multi-channel calibration method for multi-filter rotating shadow-band radiometer
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In order to improve the accuracy of solar radiation related parameters’ for crop modeling, a new calibration method (Multi-Channel Calibration) for Multi-Filter Rotating Shadow-band Radiometer (MFRSR) is proposed. It uses the Angstrom Law that links aerosol optical depth (AOD) at multiple wavelengths as the primary constraint. It also uses the bi-channel Langley Regression to provide an additional constraint. Starting with any initial guess of calibration coefficient (V0) at 870 nm, two consecutive steps, both involves calling trust region based non-linear optimization module (CONDOR), are implemented to solve (1) the intermediate parameter Angstrom coefficient and the set of biased V0s at other channels corresponding to the initial one at 870 nm channel; and (2) the final V0s of all permissible channels. The result shows that Unlike Langley method, the Multi-Channel Calibration method return V0 at all permissible channels. Besides, the new method can converge to the same (less than 0.5%) final V0s with the starting guess in a wide range. Most important, the comparison between AODs derived from those final V0s and those of AERONET sunphotometers suggests the upper limit of the error of those final V0s is less than 1.03%, which is a great improvement over the Langley V0s (7.45%).
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Maosi Chen, Maosi Chen, John Davis, John Davis, Hongzhao Tang, Hongzhao Tang, Zhiqiang Gao, Zhiqiang Gao, Wei Gao, Wei Gao, } "A multi-channel calibration method for multi-filter rotating shadow-band radiometer", Proc. SPIE 8513, Remote Sensing and Modeling of Ecosystems for Sustainability IX, 851305 (24 October 2012); doi: 10.1117/12.929454; https://doi.org/10.1117/12.929454

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