Data set from Schleich Anouk, Durrieu Sylvie, Maxime Soma and Cédric Vega, "Improving GEDI Footprint Geolocation using a High Resolution Digital Elevation Model"

We proposed a geolocation correction method for Global Ecosystem Dynamics Investigation (GEDI) data. The method, called GeoGEDI, is only based on high-resolution digital elevation models (DEMs) and GEDI derived ground elevations. The method does not need any other input, except for a DEM and GEDI Level 2A data.

For each footprint, an error map between GEDI ground estimates and reference DEM is computed, and a flow accumulation algorithm is used to retrieve the optimal footprint position.

GeoGEDI was tested on footprints in Landes and Vosges, two french forests. The method was applied to GEDI versions 1 (v1) and 2 (v2), by either a single or four full-power laser beam tracks.

This dataset is composed of 157 977 GEDI footprints whith positions of unchanged GEDI v1 and v2 releases and the optimal position calculated with our GeoGEDI algorithm.

GEDI L2A products were downloaded from NASA’s archive center : R. Dubayah, M. Hofton, J. Blair, J. Armston, H. Tang, S. Luthcke, 2020. “GEDI L2A Elevation and Height Metrics Data Global Footprint Level V001”, distributed by NASA EOSDIS Land Processes DAAC, https://doi.org/10.5067/GEDI/GEDI02_A.001.

R. Dubayah, M. Hofton, J. Blair, J. Armston, H. Tang, S. Luthcke, 2021. “GEDI L2A Elevation and Height Metrics Data Global Footprint Level V002”, distributed by NASA EOSDIS Land Processes DAAC, https://doi.org/10.5067/GEDI/GEDI02_A.002.

DEM data was downloaded from "RGE Alti 1m", disributed by IGN, https://geoservices.ign.fr/rgealti

This dataset also includes data intersected with : - Aerial lidar system Digital Surface Model of Vosges, 2020, provided by IGN
- Photogrammetric Digital Surface Model of Landes, 2018, provided by IGN
- BD Forêt V2, distributed by IGN, https://geoservices.ign.fr/bdforet

GEDI data was filtered on quality flag and full beams.

Four set ups were tested for GeoGEDI processing:
- 1_4 : GeoGEDI on GEDI v1 using 4 beams
- 2_4 : GeoGEDI on GEDI v2 using 4 beams
- 1_1 : GeoGEDI on GEDI v1 using a single beam
- 2_1 : GeoGEDI on GEDI v2 using a single beam

Variables :

• sht_ftp : shotnumber
• orbit
• beam
• deltatime
• date : deltatime as date
• studysite : Landes or Vosges
• X_wgs1 and Y_wgs1 : version 1 coordinates in WGS84 (lon_lowestmode ans lat_lowwestmode)
• X_wgs2 and Y_wgs2 : version 2 coordinates in WGS84 (lon_lowestmode ans lat_lowwestmode)

For each GEDI version the initial GEDI variables (noted 1 for v1 and 2 for v2) : - zg1 : ground elevation of GEDI : lowest_mode (with RAF18 correction to get RGF93 elevations) - rh0v1 : relative height 0% - rh98v1 : relative height 98%
- rh100v1 : relative height 100%
- selectedalgo_1 : ID of selected algorithm
- dgrdf_1 : degrade flag
- qltf_1 : quality flag
- sens_1 : sensitivity

For each GeoGEDI setup (noted 1_1, 1_4, 2_1, 2_4) :
- nb1_1 : number of neighbouring footprints used for the processing with GeoGEDI - flow1_1 : value of the cell where the Flow accumulation algorithm of GeoGEDI converges (highest value)

For each position (the initial positions of GEDI v1 and v2 and the four calculated GeoGEDI positions) : Coordinates are given in Lambert-93 (EPSG:2154) and the heights are in the associated RGF93 system. - x1 : longitude - y1 : latitude - z1 : the ground elevation from reference ALS data (mean altitude over 25m diameter circle) - h1 : the surface height from reference data (photogrammetric for Landes and ALS for Vosges), (maximum height over 25m diameter circle) - CODE_TFV1 : the BD forest type (data intersected from BD Foret) - elev_range : ALS ground elevation range (max - min) in 25m footprint