LP DAAC FAQ: G-LiHT
Posted: Tue Apr 15, 2025 5:23 pm America/New_York
Why did NASA scientists develop G-LiHT?
Merging of time-series and multi-sensor image data is a fusion process that allows scientists to study interactions between ecosystem composition, structure, and function. Equipped with this knowledge, we can better predict ecosystem responses due to land use, disturbance, and climate change.
Goddard's LiDAR, Hyperspectral, and Thermal Airborne Imager (G-LiHT) enables data fusion studies by providing coincident data in time and space, providing fine-scale (<1 m) observations over large areas that are needed for regional ecosystem studies. Mutli-sensor G-LiHT data solves a longstanding problem in data fusion studies—coregistration and analysis of data acquired at different seasons and illumination conditions, and often at different spatial resolutions.
G-LiHT lidar, passive, optical, and thermal data provide an analytical framework for the development of new algorithms to map plant species composition, plant functional types, biodiversity, biomass and carbon stocks, and plant growth. G-LiHT data are also used to initialize and validate 3-dimensional radiative transfer models, and intercalibrate Earth observing satellites.
G-LiHT was specifically designed for use with a wide range of common, general aviation aircraft in order to provide affordable, well-calibrated image data worldwide.
How intercomparable are G-LiHT acquisitions and data products?
G-LiHT data are typically acquired with the same instrument settings and flight parameters (e.g., flying altitude, and speed); however, users are strongly encouraged to refer to the metadata and ancillary data layers for specific acquisition details. G-LiHT data are acquired for specific science applications and differences between campaigns will partially reflect the different strategies for data acquisition to support the science efforts.
G-LiHT data are acquired below clouds at a nominal altitude of 335 meter (m) during various times of day and sky conditions. As a result, artifacts associated with cloud shadows and variable illumination conditions may appear in the passive optical data products, particularly on days with intermittent cloud cover.
How is G-LiHT calibrated?
Radiometric calibration and spectral characterization of G-LiHT's imaging spectrometer is performed at NASA Goddard Space Flight Center, using a tunable laser light source and Spectral Irradiance and Radiance Responsivity Calibrations using Uniform Sources (SIRCUS), a system that maintains National Institute of Standards and Technology (NIST)-traceability via transfer radiometers.
G-LiHT lidar and thermal instruments are factory calibrated.
Lidar apparent reflectance (fraction of outgoing pulse energy in a given return) is factory calibrated and corrected for ranging distance, but not for scan angle or atmospheric interactions.
How is the at-sensor reflectance product computed?
At-sensor reflectance is computed as the ratio between observed upwelling radiance and downwelling hemispheric irradiance. An empirically derived multiplier is used to correct for differences in cross-track illumination and Bidirectional Reflectance Distribution Function (BRDF).
How do I cite G-LiHT data in a paper?
Please cite G-LiHT data products in the following format:
Cook, Bruce. GLCHMT: G-LiHT Canopy Height Model Mosaic V001. 2020, distributed by NASA EOSDIS Land Processes DAAC, https://doi.org/10.5067/Community/GLIHT/GLCHMT.001. Accessed YYYY-MM-DD.
NASA's Earth Science Program promotes the full and open sharing of data with all users, in accordance with NASA's Data and Information Policy.
G-LiHT scientists are willing collaborators who will be able to share their scientific expertise, first-hand knowledge of the acquisitions, and unique insight on the interpretation of these data.
Please notify the LP DAAC of publications and presentations citing G-LiHT so that they can be added to the growing list of G-LiHT citations.
Can I request G-LiHT data acquisitions for a specific study site?
G-LiHT is a Principal Investigator-lead instrument that was designed, assembled, maintained, and flown using funds from competed research grants. The G-LiHT team is constantly proposing and acquiring new acquisitions, motivated by NASA's Earth Science mission to understand the changing climate, its interaction with life, and how human activities affect the environment.
Please contact the LP DAAC or the G-LiHT team with compelling science questions or geographic targets of opportunity that G-LiHT could address in a future science proposal.
Why do some Digital Surface Model (DSM) granules contain only three science data layers while others contain five?
Not all campaigns and flights included production of a Digital Surface Model (DSM) data product. DSM Rugosity, Aspect, and Slope are derivatives of the Canopy Height Model (CHM) and Digital Terrain Model (DTM) products which were generated for most study areas. Some flights contain only those Rugosity, Aspect, and Slope data, while others also include DSM and DSM Mean. When released, the G-LiHT Flight Metadata (GLMETA) dataset will provide detailed information on the configuration of the G-LiHT sensor for each flight.
How do I view the data in the Hyperspectral datasets (GLREFL, GLRADS, GLHYVI, GLHYANC)?
Hyperspectral datasets function similarly to a GeoTIFF, but are delivered to the user as a compressed zip file (.zip). After this file is extracted, there are two individual files. The first is a file with no extension. The second is a .hdr, or header, file. The header file is required, as it contains metadata for ENVI-format images. It is recommended that users load hyperspectral data into ENVI, although data can also be loaded into other geographic information systems through either menu options or a direct drag-and-drop.
Merging of time-series and multi-sensor image data is a fusion process that allows scientists to study interactions between ecosystem composition, structure, and function. Equipped with this knowledge, we can better predict ecosystem responses due to land use, disturbance, and climate change.
Goddard's LiDAR, Hyperspectral, and Thermal Airborne Imager (G-LiHT) enables data fusion studies by providing coincident data in time and space, providing fine-scale (<1 m) observations over large areas that are needed for regional ecosystem studies. Mutli-sensor G-LiHT data solves a longstanding problem in data fusion studies—coregistration and analysis of data acquired at different seasons and illumination conditions, and often at different spatial resolutions.
G-LiHT lidar, passive, optical, and thermal data provide an analytical framework for the development of new algorithms to map plant species composition, plant functional types, biodiversity, biomass and carbon stocks, and plant growth. G-LiHT data are also used to initialize and validate 3-dimensional radiative transfer models, and intercalibrate Earth observing satellites.
G-LiHT was specifically designed for use with a wide range of common, general aviation aircraft in order to provide affordable, well-calibrated image data worldwide.
How intercomparable are G-LiHT acquisitions and data products?
G-LiHT data are typically acquired with the same instrument settings and flight parameters (e.g., flying altitude, and speed); however, users are strongly encouraged to refer to the metadata and ancillary data layers for specific acquisition details. G-LiHT data are acquired for specific science applications and differences between campaigns will partially reflect the different strategies for data acquisition to support the science efforts.
G-LiHT data are acquired below clouds at a nominal altitude of 335 meter (m) during various times of day and sky conditions. As a result, artifacts associated with cloud shadows and variable illumination conditions may appear in the passive optical data products, particularly on days with intermittent cloud cover.
How is G-LiHT calibrated?
Radiometric calibration and spectral characterization of G-LiHT's imaging spectrometer is performed at NASA Goddard Space Flight Center, using a tunable laser light source and Spectral Irradiance and Radiance Responsivity Calibrations using Uniform Sources (SIRCUS), a system that maintains National Institute of Standards and Technology (NIST)-traceability via transfer radiometers.
G-LiHT lidar and thermal instruments are factory calibrated.
Lidar apparent reflectance (fraction of outgoing pulse energy in a given return) is factory calibrated and corrected for ranging distance, but not for scan angle or atmospheric interactions.
How is the at-sensor reflectance product computed?
At-sensor reflectance is computed as the ratio between observed upwelling radiance and downwelling hemispheric irradiance. An empirically derived multiplier is used to correct for differences in cross-track illumination and Bidirectional Reflectance Distribution Function (BRDF).
How do I cite G-LiHT data in a paper?
Please cite G-LiHT data products in the following format:
Cook, Bruce. GLCHMT: G-LiHT Canopy Height Model Mosaic V001. 2020, distributed by NASA EOSDIS Land Processes DAAC, https://doi.org/10.5067/Community/GLIHT/GLCHMT.001. Accessed YYYY-MM-DD.
NASA's Earth Science Program promotes the full and open sharing of data with all users, in accordance with NASA's Data and Information Policy.
G-LiHT scientists are willing collaborators who will be able to share their scientific expertise, first-hand knowledge of the acquisitions, and unique insight on the interpretation of these data.
Please notify the LP DAAC of publications and presentations citing G-LiHT so that they can be added to the growing list of G-LiHT citations.
Can I request G-LiHT data acquisitions for a specific study site?
G-LiHT is a Principal Investigator-lead instrument that was designed, assembled, maintained, and flown using funds from competed research grants. The G-LiHT team is constantly proposing and acquiring new acquisitions, motivated by NASA's Earth Science mission to understand the changing climate, its interaction with life, and how human activities affect the environment.
Please contact the LP DAAC or the G-LiHT team with compelling science questions or geographic targets of opportunity that G-LiHT could address in a future science proposal.
Why do some Digital Surface Model (DSM) granules contain only three science data layers while others contain five?
Not all campaigns and flights included production of a Digital Surface Model (DSM) data product. DSM Rugosity, Aspect, and Slope are derivatives of the Canopy Height Model (CHM) and Digital Terrain Model (DTM) products which were generated for most study areas. Some flights contain only those Rugosity, Aspect, and Slope data, while others also include DSM and DSM Mean. When released, the G-LiHT Flight Metadata (GLMETA) dataset will provide detailed information on the configuration of the G-LiHT sensor for each flight.
How do I view the data in the Hyperspectral datasets (GLREFL, GLRADS, GLHYVI, GLHYANC)?
Hyperspectral datasets function similarly to a GeoTIFF, but are delivered to the user as a compressed zip file (.zip). After this file is extracted, there are two individual files. The first is a file with no extension. The second is a .hdr, or header, file. The header file is required, as it contains metadata for ENVI-format images. It is recommended that users load hyperspectral data into ENVI, although data can also be loaded into other geographic information systems through either menu options or a direct drag-and-drop.