The effect of atmospheric correction on AVIRIS data to obtain consistent multiyear foliage chemistry results

During the Accelerated Canopy Chemistry Program (ACCP) study, AVIRIS data were acquired over Blackhawk Island, WI and Harvard Forest, MA to be used to assess the value of imaging spectrometer data in determining canopy chemistry constituents, in particular nitrogen and lignin. An extensive ground sample collection effort was undertaken to provide calibration for the chemical analysis. Correlations between the laboratory chemical analysis of leaves and AVIRIS 224 channel images were derived from a portion of the sample set and the ensuing calibration was used to derive nitrogen and lignin values from AVIRIS. Calibrations were derived from 1992 overflight data by multiple linear regression. However, the same calibrations applied to 1993 overflight data yielded values that were internally consistent but approximately 50% too high for both lignin and nitrogen. Incorrect atmospheric correction is considered the main cause for the discrepancy. Sensitivity tests were applied to the original data by changing multiplicative and additive atmospheric parameters. The main source of error is in the atmospheric water vapor value applied. Empirical-line correction is the most accurate method for spectral image correction