RADAR MODELING OF A BOREAL FOREST

A mixed coniferous forest stand located near Howland, Maine, has been modeled at SAR frequencies (P-, L-, and C-bands). A NASA/JPL multiple-view angle, multiple-frequency SAR was flown aboard a DC-8 aircraft on September 2, 1989. The extensive measurements of ground truth and canopy geometry parameters were performed in a 200 m-square hemlock-dominated plot inside the forest. About 10% of the trees were sampled to determine a distribution of diameter at breast height (DBH). Four representative hemlock trees with a DBH equal to 6, 12, 21.9, and 30.2 cm were destructively sampled to obtain the tree architectural and biomass data of the forest. Hemlock trees in the forest are modeled by characterizing tree trunks, branches, and needles (leaves) with randomly oriented, lossy dielectric cylinders whose area and orientation distributions are prescribed. The distorted Born approximation is used to compute the backscatter at P-, L-, and C-SAR frequencies. The input parameters to the model are determined from the analysis of ground truth and tree architectural data gathered from the experiment site. Comparison of theory results with calibrated data show that the model values are lower than the data. The experiment and model results agree quite closely, however, when the ratio of VV to HH and HV to HH are compared.