Skip to main content

The Global Ecosystem Dynamics Investigation (GEDI) instrument is a full-waveform lidar installed on the International Space Station that produces detailed observations of the 3D structure of Earth’s surface. GEDI's three lasers precisely measure forest canopy height, canopy vertical structure, and surface elevation. By accurately measuring forests in 3D, GEDI data play an important role in understanding the amounts of biomass and carbon forests store and how much they lose when disturbed.

GEDI Filenames

GEDI filenames (i.e., the local granule ID) follow a naming convention which gives useful information regarding the specific product.

In this example of a Version 2 Level 01B product, the filename GEDI01_B_2019110110221_O01997_03_T03335_02_005_01_V002.h5 indicates:

  • GEDI01_B = Product Short Name
  • 2019110 = Julian Date of Acquisition in YYYYDDD
  • 110221 = Hours, Minutes, and Seconds of Acquisition (HHMMSS)
  • O01997 = O = Orbit, 01997 = Orbit Number
  • 03 = Sub-Orbit Granule Number
  • T03335 = T = Track, 033335 = Track Number
  • 02 = Positioning and Pointing Determination System (PPDS) type (00 is predict, 01 rapid, 02 and higher is final)
  • 005 = PGEVersion = SDPS Release Number
  • 01 = Granule Production Version
  • V002 = Version Number
  • .h5 = Data Format

In this example of a Version 2 Level 01A product, the filename GEDI02_A_2019110014613_O01991_01_T04905_02_003_01_V002.h5 indicates:

  • GEDI02_A = Product Short Name
  • 2019110 = Julian Date of Acquisition in YYYYDDD
  • 014613 = Hours, Minutes, and Seconds of Acquisition (HHMMSS)
  • O01991 = O = Orbit, 01991 = Orbit Number
  • 01 = Sub-Orbit Granule Number
  • T04905 = T = Track, 04905 = Track Number
  • 02 = Positioning and Pointing Determination System (PPDS) type (00 is predict, 01 rapid, 02 and higher is final)
  • 003 = PGEVersion = SDPS Release Number
  • 01 = Granule Production Version
  • V002 = Version Number
  • .h5 = Data Format

In this example of a Version 2 Level 02B product, the filename GEDI02_B_2019110045136_O01993_01_T02061_02_003_01_V002.h5 indicates:

  • GEDI02_B = Product Short Name
  • 2019110 = Julian Date of Acquisition in YYYYDDD
  • 045136 = Hours, Minutes, and Seconds of Acquisition (HHMMSS)
  • O01993 = O = Orbit, 01993 = Orbit Number
  • 01 = Sub-Orbit Granule Number
  • T02061 = T = Track, 02061 = Track Number
  • 02 = Positioning and Pointing Determination System (PPDS) type (00 is predict, 01 rapid, 02 and higher is final)
  • 003 = PGEVersion = SDPS Release Number
  • 01 = Granule Production Version
  • V002 = Version Number
  • .h5 = Data Format

GEDI Product Long Name

The GEDI Product Long Name (i.e., Collection-Level) convention provides useful information regarding all GEDI products.

Below is an example of a GEDI Level 1B product. All GEDI Product Long Names for Version 2 follow the same basic structure.

The GEDI L1B Geolocated Waveform Data Global Footprint Level V002 collection has the following characteristics:

  • GEDI – Instrument
  • L1B – Processing Level
  • Geolocated Waveform Data – Geophysical Parameter
  • Global – Global Coverage
  • V002 – Version

The location of the ranging point (also referred to in this document as a bounce point) can be commonly described in terms of geodetic latitude, longitude, and height above a reference ellipsoid, or it can be represented in Cartesian coordinates in an Earth Centered Inertial (ECI) or Earth Centered Fixed (ECF) reference frame.

Several reference frames are used in the precise positioning and precise pointing required for geolocation of GEDI footprints. The Space Station Analysis Coordinate System (SSACS) and GEDI frame are used to orient instruments relative to one another. The Optical Bench Frame (OBF) provides a connection to the GEDI frame and a reference system for targeting calculations. Star tracker frames connect these to the ECI frame allowing conversion to geodetic coordinates.

GEDI Processing Levels

LP DAAC distributes GEDI land data processed to Level 1 and Level 2:

  • Level 1A: Raw Waveforms (not publicly available)
  • Level 1B: Geolocated Waveforms
  • Level 2A: Ground Elevation, Canopy Top Height, Relative Height Metrics
  • Level 2B: Canopy Cover Fraction (CCF), CCF profile, Leaf Area Index (LAI), LAI profile

GEDI Processing Description

GEDI science data products include footprint and gridded data products that describe the 3-dimensional features of the Earth. These data products are assigned different levels, which indicate the amount of processing that the data has undergone after collection. All products are publicly available, with the lower level products (L1 and L2) from LP DAAC and the higher level (L3 and L4) products from the Oak Ridge National Laboratory Distributed Active Archive Center (ORNL DAAC). Data are initially transferred to the GEDI Mission Operations Center (MOC) at the Goddard Space Flight Center, which deploys weekly acquisition planning, and then processed through the Science Operations Center (SOC) to distribute science data products to the above DAACs.

The physical theories, mathematical procedures, and model assumptions that are used in the creation of these data products are described in the Algorithm Theoretical Basis Documents (ATBDs).

GEDI products have two sources of metadata: the embedded HDF5 metadata and the external ECS metadata. The HDF5 metadata contains valuable information, including global attributes and dataset specific attributes pertaining to the granule. The ECS (generated by the EOSDIS Core System) .met file is the external metadata file in XML format, which is delivered to the user along with the GEDI product. It provides a subset of the HDF metadata.

The dataset attributes contain specific SDS information, such as the data range and applicable scaling factors for the data. The LP DAAC data products page provides these details within a concise document for each of the products. An HDF5 file also contains core metadata essential for search services. It should be noted that it is difficult for a standard HDF call to interpret HDF5 geolocation or temporal information without further knowledge of the file structure.

Learn more about GEDI

Instrument Type

Altimeter

Instrument Subtype

Lidar/laser altimeter

Specifications

Resolution

Spatial

3 lasers produce a total of 8 beam ground transects, which consist of ~30 meter (m) footprint samples spaced approximately every 60 m along-track

Spectral

1 m

Related Data Centers/Projects

LP DAAC

NASA's Land Processes Distributed Active Archive Center provides data crucial to the investigation, characterization, and monitoring of biological, geological, hydrological, ecological, and related conditions and processes.
GEDI

The Global Ecosystem Dynamics Investigation (GEDI) project focuses on how deforestation has contributed to atmospheric CO2 concentrations, how much carbon forests will absorb in the future, and how habitat degradation will affect global variability of life.

Frequently Asked Questions

Earthdata Forum

Our online forum provides a space for users to browse thousands of FAQs about research needs, data, and data applications. You can also submit new questions for our experts to answer.

Submit Questions to Earthdata Forumand View Expert Responses

Earthdata
Forum