A procedure for the correction of the effect of variation in incidence angle on AIRSAR data

Radar imaging is a valuable tool for the monitoring and management of tropi cal ecosystems. One of the obstacles to its successful usage is the variati on of the radar backscatter with incidence angle caused by the side-looking mode of the sensor. Available research has modelled the effect of changes in incidence angle for soil, grass and scattering mechanisms in tree-covere d areas. The effect varies depending on the scattering mechanism. To model the radar backscatter behaviour of a natural landscape, therefore, implies precise knowledge of the land-cover composition. A method for estimating an d correcting the effect of changes in look angle on backscatter data is con sequently proposed; it requires little field knowledge and encompasses the effects on most land-cover types in the study area. The method is based on the assumption that each line in azimuth direction contains a similar compo sition in regard to land-cover types. The backscatter frequency distributio n of each azimuth line can then be employed to model and correct for the ef fect of variation in incidence angle. The results are evaluated using an ex isting land-cover classification to extract mean backscatter values for ind ividual land-cover classes before and after the correction procedure. The c orrection procedure is shown to successfully adjust backscatter intensities to a nominal incidence angle for the vegetation communities in a coastal t ropical savanna landscape in Australia's Northern Territory.