A method of upscaling ground measurements of Leaf Area Index based on Taylor Series expansion Model
The ground measurements of Leaf Area Index (LAI) are usually used to validate the LAI estimated using remote sensing observations. The main problem encountered in the validation is the scale mismatch between the sampling area of ground measurements and coarse-resolution image pixel, especially when those sampling area are not ideal homogenous. This study introduced a new approach of upscaling ground measurements to the coarse-resolution scale for the validation of LAI estimations. This upscaling method was based on the Taylor Series expansion Model (TSM). The high-resolution images were used to provide auxiliary information at the sub-pixel scale of coarse-resolution image pixel. The possible error associated with this method is derived from the neglection of the third- and higher-order TSM terms and the uncertainty of the empirical model. The upscaled ground measurements with upscaling error smaller than half of eigenaccuracy could be used for validation of LAI estimations with coarse resolution.