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Zhang Xin , Zhao Xiang, Liu Suhong Beijing Normal University

A METHOD FOR THE RETRIEVAL OF AEROSOL OPTICAL THICKNESS on CBERS data from top-of-atmosphere radiance. Zhang Xin , Zhao Xiang, Liu Suhong Beijing Normal University. CONTENTS. Background Method Validation Summary. Background. Water.

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Zhang Xin , Zhao Xiang, Liu Suhong Beijing Normal University

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  1. A METHOD FOR THE RETRIEVAL OF AEROSOL OPTICAL THICKNESS on CBERS data from top-of-atmosphere radiance Zhang Xin, Zhao Xiang, Liu Suhong Beijing Normal University

  2. CONTENTS • Background • Method • Validation • Summary

  3. Background Water • The atmospheric influence is strong enough to substantially modify the electromagnetic signal, causing the loss or the corruption of part of the carried information about the observed target. It is important to retrieve the Aerosol Optical Thickness (AOT). Vegetation

  4. Background we have developed a novel retrieval algorithm only use the visible and near-infrared (VNIR) spectral bands and have a high-accuracy Some algorithms need densely vegetated area Some algorithms currently require visible to short-wave spectral bands (400-2500nm) Some algorithms only retrieval one result on every image, it is hard to fulfill the Correction accuracy

  5. Background This method is design for CBERS CCD Image. 24 June 2007(Path 8/Row 61) , Shanxi Province, China

  6. METHOD This retrieval work is designed to obtain the main atmospheric parameters from the image itself.

  7. METHOD Calibration L=DN/K (http://www.cresda.com/) Grid divison The image is divided in 10KM*10KM cells. Selecting the suitable pixels by Cv

  8. METHOD 1. We set the surface reflectance values as the follow equation 2. C is the vegetation coverage which is decided by the Atmospherically Resistant Vegetation Index (ARVI, Kaufman and D. Tanre,).

  9. Method 1. We set the surface reflectance values as the follow equation The ρis calculated through AOT and the apparent radiance L by using radiative transfer equation. A one - dimensional search method was used to get the optimal solution.

  10. Method

  11. Validation Surface reflectance AOT Apparent reflectance Retrieval AOD

  12. Validation

  13. Validation When we get the AOT, do a atmospheric correction to get the surface reflectance. Calculate the RMSE between the retrieval reflectance and the real reflectance. The result is shown on the form.

  14. Validation Before After

  15. Validation AND Summary Vegetation Water The result after correction is much closer to the real spectrum.

  16. Summary The shortage of current work: We don’t do a lot of validation on this method, especially on CBERS image. In the next work we will download a lot of CBERS image to validation and improve this method. The vegetation coverage also has some error when VIS is small. We want to find a new algorithm to calculate it.

  17. Thank you!

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