High-resolution mapping of pantropical canopy height by integration of GEDI and TanDEM-X Data

High-resolution mapping of pantropical forest structure and biomass at high accuracy and resolution is key to quantifying carbon storage and change in the global carbon budget, and is central to the goals of the NASA Carbon Monitoring System (CMS). Since the launch of the Global Ecosystem Dynamics Investigation (GEDI) mission a first of its kind spaceborne laser specifically designed to measure vertical forest structure in April 2019, an unprecedented number of measurements are available between 51.6 N&S latitude for large area mapping. However, GEDI is a sampling mission and fusion with data from satellite imaging data is required for high spatial resolution (25-100 m) mapping. We present here a novel fusion and adaptive modelling approach developed in collaboration with the German Space Agency (DLR) that combines billions of GEDI measurements with high resolution InSAR data acquired between 2010 and 2019 by TanDEM-X, resulting in canopy height estimates at 25 and 100 m with accuracies greater than could be achieved by either alone. We found that the addition of GEDI measurements improved TanDEM-X canopy height RMSE by ~32-43% and reduced the magnitude of systematic deviations observed using TanDEM-X alone. Our fusion approach is being applied to produce 25 m and 100 m national-scale canopy height maps with known error estimates across the pantropics, including countries such as Gabon, Mexico and Australia. These fine resolution maps are currently being shared with stakeholders through the Ecometrica webmapping platform, with a view to facilitating improvements to national-scale carbon accounting and other monitoring, reporting and verification (MRV) activities in pantropical countries (e.g., Forests 2020).