Beware of per-pixel characterization of land cover

A simulation experiment was carried out to analyse the effects of the modul ation transfer function on our ability to estimate the proportions of land cover within a pixel by linear mixture modelling. In the simulated landscap e the proportion of each land cover type in every pixel was known exactly. The standard error of the estimate (SEE) between percentages derived from m ixture modelling and the actual land cover percentages was 11%. Substantial improvements in estimating the percentages can be obtained simply by deriv ing estimates for pixels of twice the original dimensions, the SEE dropping to 4.16%, though this is with the obvious consequence of a final product w ith a coarser spatial resolution. Alternatively by deconvolving the input b ands using a linear approximation of the point spread function the SEE can be reduced by almost as much, namely to 5.11%. If we combine the two approa ches, by first doconvolving the bands, estimating the percentages and then aggregating resultant pixels to twice their original linear dimensions, the SEE drops to 2.24%.