Derivation of Soil Line Influence on Two-Band Vegetation Indices and Vegetation Isolines

Abstract

This paper introduces derivations of soil line influences on two-band vegetation indices (VIs) and vegetation isolines in the red and near infra-red 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.

Soil Line Influences on Two-Band Vegetation Indices and Vegetation Isolines: A Numerical Study

“…The first trend indicates that the variations of the VIs show a similar trend to the soil line parameters. This motivated us to derive and quantify the variations of VIs in terms of the soil line parameters in our previous work [1]. There are clear trends that govern the effects of soil line variations on the VIs, which are the focus of our analyses in the next section.…”

“…The first objective is to validate the derived expressions [1]. In [1] we have showed that soil line variation influences on VIs almost linearly.…”

“…The first objective is to validate the derived expressions [1]. In [1] we have showed that soil line variation influences on VIs almost linearly. It needs to be validated and confirmed to fulfill the gap between the theoretical work and practical applications of satellite data processing.…”

“…In Section 4, the variations of the vegetation isolines and the VIs are demonstrated numerically based on the obtained soil line parameters. In Section 5, the variations of the NDVI, as an example, are shown and analyzed with the analytical formulations derived in [1] as a function of the perturbation variables related to the soil line parameters (for the purpose of validating the linearity shown by our previous work.) Finally (Section 6), we present a hypothetical case study and demonstrate an evaluation technique of soil line influences on the VI.…”

“…Our previous work [1] introduced the derivations of soil line influences on two-band VIs and the vegetation isolines. Variations of the VIs were derived analytically based on the vegetation isoline equations [37,38] by employing the slope and offset of the soil line as parameters.…”