An analysis of speckle from forest stands with periodic structures

The azimuth time signal of the backscatter measured by an airborne (incoherent or coherent) radar system is known, theoretically to contain information on the fine-scale spatial arrangement of scatterers, and this information can be revealed by an analysis of speckle. It is shown theoretically that the autocorrelation function of the small-scale (subresolution cell) backscatter signature in azimuth can be estimated from the averaged power density spectrum of azimuth (speckle) signals from homogeneously distributed targets. The accuracy of this estimate is indicated. The minimum size of statistical spatial details that can be resolved from the power spectrum, however, is fundamentally limited to the half-antenna length. The results of experiments conducted with an X-band SLAR over forest plantations with regular tree row spacing are shown to be in good agreement with theory. The row spacing could be estimated accurately using an antenna with an effective length of 2 m and an azimuth spatial resolution on the order of 25 m