A COMPARISON OF FOREST CANOPY MODELS DERIVED FROM LIDAR AND INSAR DATA IN A PACIFIC NORTHWEST CONIFER FOREST

Active remote sensing technologies, including interferometric radar (InSAR) and airborne laser scanning (LIDAR) have the potential to provide accurate information relating to three-dimensional forest canopy structure over extensive areas of the landscape. In order to assess the capabilities of these alternative systems for characterizing the forest canopy dimensions, canopyand terrain-level elevation models derived from multi-frequency InSAR and high-density LIDAR data were compared to photogrammetric forest canopy measurements acquired within a Douglas-fir forest near Olympia, WA. Canopy and terrain surface elevations were measured on large scale photographs along two representative profiles within this forest area, and these elevations were compared to corresponding elevations extracted from canopy models generated from X-band InSAR and high-density LIDAR data. In addition, the elevations derived from InSAR and LIDAR canopy models were compared to photogrammetric canopy elevations acquired at distinct spot elevations throughout the study area. Results generally indicate that both technologies can provide valuable measurements of gross canopy dimensions. In general, LIDAR elevation models acquired from high-density data more accurately represent the complex morphology of the canopy surface, while InSAR models provide a generalized, less-detailed characterization of canopy structure. The biases observed in the InSAR and LIDAR canopy surface models relative to the photogrammetric measurements are likely due to the different physical processes and geometric principles underlying elevation measurement with these active sensing systems.