An application of airborne hyperspectral and EO-1 Hyperion data for inter-sensor calibration of vegetation indices for regional-scale monitoring

In order to use satellite data from multiple sensors for monitoring of the Earth´s vegetation, satellite data product continuity and compatibility need to be investigated. In this study, we assessed inter-sensor compatibility of the normalized difference vegetation index (NDVI) by simulating bandpasses of the NOAA-14 AVHRR, Terra-MODIS, and Landsat-7 ETM+ from airborne hyperspectral and EO-1 Hyperion data acquired over a savanna-forest transitional zone in Brazil. Our results showed that the simulated reflectances among the sensors examined here were near-linearly related, but with relationships that were land cover-dependent, e.g., reflectances over green vegetation targets formed separate relationships. The deviations were larger for greener targets. On the other hand, the NDVI crossplots among the sensors formed single, land-cover independent relationships. They were, however, curve-linearly related with the degree of curve-linearity increasing with atmosphere contamination. Also, land cover dependencies appeared in the NDVI cross-plots when contaminated by atmosphere. These results suggest that inter-sensor calibration and continuity of the NDVI are achievable, but require a careful examination of surface and atmospheric conditions and the development of a theoretical basis.