High spatial resolution QuickBird satellite data have provided new opportunities for remote sensing applications in agriculture. In this study, image-based algorithms for atmospheric correction were evaluated on QuickBird imagery for retrieving surface reflectance (ρλ) of corn and potato canopies in Minnesota. The algorithms included the dark object subtraction technique (DOS), the cosine approximation model (COST), and the apparent reflectance model (AR). The comparison with ground-based measurements of canopy reflectance during a 3-year field campaign indicated that the AR model generally overestimated ρλ in the visible bands, but underestimated ρλ in the near infrared (NIR) band. The DOS-COST model was most effective for the visible bands and produced ρλ with the root mean square errors (RMSE) of less than 0.01. However, retrieved ρλ in the NIR band were more than 20% (mean relative difference or MRD) lower than ground measurements and the RMSE was as high as 0.16. The evaluation of the COST model showed that atmospheric transmittance (Tλθ) was substantially overestimated on humid days, particularly for the NIR band because of the undercorrection of water vapor absorption. Alternatively, a contour map was developed to interpolate appropriate Tλθ for the NIR band for clear days under average atmospheric aerosol conditions and as a function of precipitable water content and solar zenith angle or satellite view angle. With the interpolated Tλθ, the accuracy of NIR band ρλ was significantly improved where the RMSE and MRD were 0.06 and 0.03%, respectively, and the overall accuracy of ρλ was acceptable for agricultural applications.
Bibliographical noteFunding Information:
The authors wish to acknowledge a grant from USDA/NASA 2001-52103-11321 for providing QuickBird images and a grant from the University of Minnesota Graduate School Grant-In-Aid for supporting ground measurement. We greatly thank Dr. Susan Moran for sharing atmospheric optical data measured at Maricopa, Arizona, and three anonymous reviewers for their constructive suggestions. We also thank Dr. Carl Rosen and Mr. Frank Kasowski for providing field sites, Dr. Yi Zhang, Dr. Kurt Spokas, and Mr. Matt McNearney for general assistance with ground measurements.
- Atmospheric correction
- Surface reflectance