At this very moment, approximately 220 miles above the Earth, lasers from the Global Ecosystem Dynamics Investigation (GEDI) instrument on the International Space Station (ISS) are firing 242 times per second, illuminating 25-meter footprints on the Earth’s surface, and taking systematic and detailed 3D measurements of forest canopy height, forest structure, and surface elevation.
Since the initial release of GEDI Level 1 and Level 2 data in January 2020, these three-dimensional assessments of the Earth’s terrestrial biomes have enhanced the ecological research community’s investigations of planet’s most diverse environments. Now, NASA’s Oak Ridge National Laboratory Distributed Active Archive Center (ORNL DAAC) has released the first Level 4 data from the GEDI mission, which is sure to benefit ecological research even more.
“This is the first time that aboveground biomass density (AGBD) estimates are available at this level of detail for tropical and temperate forests across the world,” said Dr. Rupesh Shrestha, a research staff member at the ORNL DAAC. “Distribution of aboveground biomass (or carbon) and how it interacts with the changing climate and other disturbances is not well understood. GEDI provides globally consistent measurements and algorithms and helps to overcome the uncertainties in AGBD estimates.”
The models used to produce Level 4A data were developed with field estimates of AGBD collocated with simulated GEDI waveforms from discrete-return airborne lidar and used a quality-filtered calibration dataset that contains 8,587 simulated waveforms in 21 countries. The GEDI approach to developing footprint AGBD models considers multiple candidates stratified by world region and plant functional type (PFT) with different functional forms. The footprint models represent the following combination of PFTs: deciduous broadleaf trees, evergreen broadleaf trees, evergreen and deciduous needleleaf trees, and combinations of woodlands, grasslands, and shrubs.
The Level 4A dataset consists of 6,742 files in HDF5 format and covers the period from April 18, 2019, to September 2, 2020. These files include more than 5 billion land surface shots (measurements), which is orders of magnitude more than any previous global biomass study. The Level 4A product also contains all the ancillary information necessary to reproduce the AGBD prediction for individual GEDI measurements from Level 2A data.
About the GEDI Mission
Launched on December 2018 and installed on the ISS’s Japanese Experiment Module-Exposed Facility, GEDI is a full waveform lidar (i.e., laser version of radar) instrument offering the highest resolution and densest sampling of any lidar ever put in orbit. Led by scientists at the University of Maryland, the mission is supported by NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
The GEDI instrument produces high-resolution laser ranging observations of the 3-dimensional structure of the Earth. Its data are transferred to the GEDI Mission Operations Center and then processed through the Science Operations Center, both of which are located at Goddard, and then sent to two NASA Earth Observing System Data and Information System (EOSDIS) Distributed Active Archive Centers (DAACs) where they are archived, managed, and distributed to a diverse worldwide user community.
The GEDI mission has published three previous datasets. The first, lower-level datasets — a Level 1B product that provides geolocated waveforms and Level 2A and 2B products providing canopy height and canopy profile metrics at the footprint level — were made available in January 2020 through NASA’s Land Processes DAAC (LP DAAC), a partnership between NASA and the USGS that manages, archives, and distributes EOSDIS land processes data, services, and tools for discovering and analyzing data.
Along with the GEDI Level 3 dataset released earlier this year, the GEDI Level 4A dataset is available from ORNL DAAC, a partnership between NASA and the U.S. Department of Energy that is responsible for collecting, archiving, and distributing EOSDIS data related to biogeochemical dynamics, ecological data, and environmental processes. The AGBD estimates and footprint models of the GEDI Level 4A dataset will be used as inputs for the ORNL DAAC’s forthcoming Level 4B data product, which will provide gridded estimates of AGBD and associated uncertainty at 1km grids.
In addition to collecting, archiving, and distributing EOSDIS data related to biogeochemical dynamics, ecological data, and environmental processes, the ORNL DAAC also provides a variety of data subsetting and visualization tools that allow users to analyze and explore available data products, including those from GEDI and other missions.
GEDI Level 4A data will be available for subsetting in the ORNL DAAC’s Global Subsets Tool, which allows users to select a location and get subsets and time series visualizations covering up to 200 km x 200 km for the selected NASA data products. GEDI Level 4A data will also be available in NASA's Earthdata Cloud, which gives users the opportunity to access and process large quantities of data, and promotes opportunities for innovation around new services, such as sequencing data to support machine learning and artificial intelligence.
The extended processing capabilities offered by the Earthdata Cloud will undoubtedly be a benefit to those working with the GEDI mission’s expansive data. During its lifetime, GEDI is expected to provide more than 10 billion of land surface measurements, which, in addition to providing a wealth of information on the structure and canopy height of the world’s forests, will generate invaluable calibration information for other missions, such as the upcoming NASA-Indian Space Research Organisation SAR (NISAR) Mission, which will measure Earth’s changing ecosystems, dynamic surfaces, and ice masses providing information about biomass, natural hazards, sea level rise, and groundwater.
For decades, studies of Earth’s terrestrial ecosystems have relied on two-dimensional satellite data and limited field studies and sampling from ground-based and airborne lidar. That began to change with the initial releases of GEDI data. Now, with this new GEDI Level 4A dataset published through ORNL DAAC offering footprint level estimates of AGBD, scientists engaged in ecological research will have even more high-resolution data to inform their investigations.
To learn more about the GEDI mission and GEDI data products, see the following online resources:
Article: New, Gridded Level 3 Data Product Facilitates the Use of GEDI Mission Data
GEDI data can be searched for and discovered using the EOSDIS Earthdata Search application.
Information about using the Earthdata Cloud is available on NASA's Earthdata website.
LP DAAC GEDI Landing Pages:
ORNL DAAC GEDI Landing Page: