Digital Elevation Models (DEMs) and lava outlines from the Litla-Hrútur eruption, Iceland, July 2023

Introduction:

On the 10th of July 2023, at 16:40, an eruption started in the Reykjanes Peninsula, Iceland, next to the mountain "Litla-Hrútur". As part of the response, the CIEST² french initiative was activated (Gouhier et al., 2022). Once activated, Pléiades stereoimages were tasked and scheduled for fast delivery within the area of Interest.

Once acquired and delivered, the Pléiades images are processed following the methods described in the section below. This repository contains the near-real time results of DEMs, difference maps compared to a pre-eruption DEM, and lava outlines digitized from the difference map and the orthoimage.

This repository is currently in construction and will be updated during the time period where the Pléiades stereoimages are being acquired.

Methods:

The Pléiades stereoimages were processed using the Ames StereoPipeline (ASP, Shean et al., 2016, see ASP branch in repository), yielding a DEM in 2x2m GSD and an orthoimage in 0.5x0.5m GSD. The processing was done using as only input the stereoimages and their orientation information, as Rational Polynomial Coefficients (RPCs). The parallel_stereo routine performs all the steps needed in the correlation of the stereoimages, yielding a pointcloud which is then interpolated using the routine point2dem. Besides default parameters, the parallel_stereo parameters used for creation of the DEMs were the standard parameters, plus the following ones: 

--stereo-algorithm asp_mgm --corr-tile-size 300 --corr-timeout 900 --cost-mode 3 --subpixel-mode 9 --corr-kernel 7 7 --subpixel-kernel 15 15

Once the DEM was created, DEM co-registration was applying in order to align and minimize positional biases between the pre-eruption DEM and the Pléiades DEMs. We followed the co-registration method of Nuth & Kääb (2011), implemented by David Shean’s co-registration routines (https://github.com/dshean/demcoreg, Shean et al., 2016). The co-registration involved a horizontal and vertical shift of the Pléiades DEMs, as well as a planar tilt correction. The horizontal offset obtained from the DEM co-registration was also applied to the Pléiades orthoimages.

The pre-eruption DEM used for this study is the IslandsDEMv1 (National Land Survey of Iceland)

Lava outlines were manually digitized from the co-registered Pléiades orthoimages, The lava outlines are available as GeoPackages in the “GPKG” branch of the repository.

At the moment, the results from Pléiades are not being used to estimate lava volumes or lava effusion rate, since the area is covered with a significant amount of smoke that causes a large blur in the images, and the map of elevation difference shows outliers within and outside the lavas, therefore it's not guaranteed that the volumes estimated would be unbiased.

Data Specifications:

• Cartographic projection: ISN93 / Lambert 1993 (EPSG:3057, https://epsg.io/3057)
• Origin of Elevation: meters above GRS80 ellipsoid (WGS84)
• Raster data format: GeoTIFF
• Raster compression system: LZW
• Vector data format: GeoPackage (https://www.geopackage.org/)
• Pléiades dataset includes only DEMs because the Pléiades ortho imagery is for licensed use only. Please contact the authors for further information on this.

Acknowledgements: 

Pléiades images were provided under the CIEST² initiative (CIEST² is part of ForM@Ter (https://en.poleterresolide.fr/) (image Pléiades©CNES2023, distribution AIRBUS DS) 

Dataset Attribution 

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