Interpreting ERS SAR signatures of agricultural crops in Flevoland, 1993-1996

This paper discusses an analysis of ERS SAR imagery of agricultural crops i n Flevoland, The Netherlands, over a four-year period (1993 to 1996) to stu dy the stability of multi-temporal radar signatures from one year to the ne xt. Direct comparisons of the multitemporal profiles of crop signatures are made to derive limits on their stability and to examine the differences be tween them from one year to the next, Sharp rises (of several dB) in tempor al crop signatures are linked to variations in rainfall, freezing, and inci dent angle (due to imaging passes from different orbit tracks). Model simul ations confirm the plausibility of these mechanisms and emphasize their imp ortance for quantitative monitoring of agricultural crop development, The p ossibility of timing critical phases of the crop growth cycle is highlighte d using field-to-field variations with particular regard to the emergence a nd closure of sugarbeet. The interyear comparison also enables generalized comments to be made regarding the performance and stability of crop classif ication algorithms from one year to another, Only summer months are consist ently identified as helping to distinguish broad-leaved crops from cereals. There is some evidence that other times of the year assist in distinguishi ng specific crops, but this evidence is not stable from one year to another .