Derivation of soil line influence on two-band vegetation indices and vegetation Isolines

This paper introduces derivations of soil line influences on two-band vegetation indices (VIs) and vegetation isolines in the red and near infrared reflectance space. Soil line variations are described as changes in the soil line parameters (slope and offset) and the red reflectance of the soil surface. A general form of a VI model equation written as a ratio of two linear functions (e.g., NDVI and SAVI) was assumed. It was found that relative VI variations can be approximated by a linear combination of the three soil parameters. The derived expressions imply the possibility of estimating and correcting for soil-induced bias errors in VIs and their derived biophysical parameters, caused by the assumption of a general soil line, through the use of external data sources such as regional soil maps. © 2009 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland