Evaluation of the Potential of NASA GEDI Data for the Analysis of Vertical Vegetation Structure

Abstract Accurate knowledge of vegetation structure is crucial for many aspects of the scientific study of ecosystems. LiDAR is a leading technology for efficiently capturing vegetation structure and plays an important role in forestry and forest science. LiDAR systems can operate from a variety of platforms, including tripods, vehicles, UAVs (uncrewed aerial vehicles), airplanes, and satellites. Depending on the platform, the spatial resolution, data acquisition effort, and coverage area vary significantly. Since 2019, satellite-based LiDAR data from NASA’s Global Ecosystem Dynamics Investigation (GEDI) mission has offered a freely available, global alternative for assessing vegetation structure on regional or global scales. This paper investigates the potential of GEDI data for describing vertical vegetation structure. To assess GEDI’s capabilities, the three key forest metrics canopy height, canopy cover, and plant area volume density (PAVD) obtained from GEDI waveforms were compared to metrics and pseudo-waveforms derived from airborne laser scanning (ALS, both full-waveform (FW) and discrete return (DR)) and terrestrial laser scanning (TLS) data for eight GEDI shots situated in the study area near Dresden, Germany. The comparison of canopy height and canopy cover estimates between GEDI and the reference datasets (ALS and TLS) indicated varying levels of agreement across the shots. RMSE values for canopy height were 5.97 m (GEDI vs. ALS-FW), 6.17 m (GEDI vs. ALS-DR), and 6.21 m (GEDI vs. TLS), while canopy cover RMSE values were 0.34, 0.32, and 0.32, respectively. The comparison of canopy metrics, waveform and PAVD representations at the shot level highlights limitations of GEDI, including geolocation uncertainty and vertical accuracy, for fine scale applications.