Influences of Soil Line Parameters on Soil Brightness Estimation with Soil Isoline Equations in Red-Nir Reflectance Subspace

Estimation of soil brightness from a reflectance spectrum involves a radiative transfer model that describes a canopy-soil system of layers. An assumption of soil line in the model becomes a source of error for the estimation of soil brightness. This study investigates the influences of soil line parameters (slope and NIR intercept) on estimation of soil brightness underneath the vegetation canopy. The investigation was carried out based on a theory of inter-band relationship under the constant soil brightness, which is known as the soil `isoline' equations. Simulation datasets from EO-l/Hyperion hyperspectral data were used to compare inversion results by varying the intercept and slope of the soil line. The result indicates several trends of the brightness estimation caused by the variations of soil line parameters. Since the soil line is known to be varied sensor by sensor, the trends clarified in this study would be beneficial to calibration of multiple soil isoline equations for inter-sensor calibration of the satellite sensors in the context of mega satellite constellation.