Refined empirical line method to calibrate IKONOS imagery (Q2508213)

To extract quantitative biophysical parameters such as leaf biomass and leaf chlorophyll concentration from the remotely sensed imagery, the effect of atmospheric attenuation must be removed. The Refined Empirical Line (REL) method was used to calibrate the IKONOS multispectral imagery. The IKONOS digital numbers were converted to the at-satellite reflectance, then the linear relation between at-satellite reflectance and surface spectral reflectance \((\rho_\lambda)\) was derived from six bright targets of known reflectance in the image, and modelled estimates of the image reflectance at \(\rho_\lambda=0\). Validation targets were used to test the feasibility of REL method. The mean relative errors between \(\rho_\lambda\) retrieved from IKONOS image using REL method and ground-measured \(\rho_\lambda\) were 11\%, 13\%, 3\% and 5\% in the IKONOS blue, green, red and near-infrared respectively. When dark targets are unavailable or measurement of dark target is inconvenient, the REL method was most crucial for retrieving surface spectral reflectance. The REL offers a simple approach for quantitative retrieval of biophysical parameters from IKONOS imagery.