Spot6 and Pléiades Digital Elevation Models (DEMs) and elevation change grid to understand the South Lhonak lake (Sikkim) flood of October 2023

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Introduction

On 3 October 2023, a multi-hazard cascade in the Sikkim Himalaya, India, was triggered by the collapse of a frozen lateral moraine into South Lhonak Lake

We share here the SPOT6 and Pléiades DEMs and the elevation change maps derived from these images. The collection includes four files:

Two pre-event DEMs from SPOT6

2018-12-01_Lhonak_DEM_SGM_4m_on_Cop30_BiasCorr_NoData_aligned.tif

2018-12-08_Lhonak_DEM_SGM_4m_on_Cop30_BiasCorr_NoData_aligned.tif

One post-event mosaic DEM from Pléiades 

Post-Event_DEM_SGM_october2023.tif

One grid of elevation change from 2018 to 2023

dh_mosaic_Lhonak_SGM_median.tif

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Methods

The SPOT6 and Pléiades stereo-images were processed using the Ames Stereo Pipeline (ASP, Beyer et al., 2018), yielding a DEM in 4x4 m GSD. The processing was done using as only input the stereo-images and their orientation information, as Rational Polynomial Coefficients (RPCs). The parallel_stereo routine performs all the steps needed in the correlation of the stereo-images, yielding a pointcloud which is then interpolated using the routine point2dem. We used the semi global matching algorithm and the set of processing parameters from Deschamps-Berger et al. (2020)

Beyer, R. A., Alexandrov, O., and McMichael, S.: The Ames Stereo Pipeline: NASA’s Open Source Software for Deriving and Processing Terrain Data, Earth and Space Science, 5, 537–548, https://doi.org/10.1029/2018EA000409, 2018.

Deschamps-Berger, C., Gascoin, S., Berthier, E., Deems, J., Gutmann, E., Dehecq, A., Shean, D., and Dumont, M.: Snow depth mapping from stereo satellite imagery in mountainous terrain: evaluation using airborne laser-scanning data, The Cryosphere, 14, 2925–2940, https://doi.org/10.5194/tc-14-2925-2020, 2020.

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Data Specifications:

Cartographic projection: UTM zone 45N (EPSG:32645)

Origin of Elevation: meters above WGS84 ellipsoid

Raster data format: GeoTIFF

NoData value : -9999

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Acknowledgements:

Pléiades and SPOT6 images were acquired thanks to the CIEST2 service developed and performed with the French Space Agency (CNES) by FormaTerre, Solid Earth component of the Data Terra Research Infrastructure

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Dataset Attribution:

This dataset is licensed under a Creative Commons CC BY-NC 4.0 International License (Attribution-NonCommercial).