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

<strong>Introduction:</strong> 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. <strong>Methods</strong>: 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 <em>parallel_stereo </em>routine performs all the steps needed in the correlation of the stereoimages, yielding a pointcloud which is then interpolated using the routine <em>point2dem</em>. Besides default parameters, the <em>parallel_stereo</em> parameters used for creation of the DEMs were the standard parameters, plus the following ones: <em>--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</em> 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 &amp; 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 used by the Institute of Earth Sciences of the Univesity of Iceland (Jarðvisindustofnun Háskoli Íslands) to estimate lava volumes and effusion rate, following the methods described in Pedersen et al. (2022). Please contact the authors if these data are intended to be used for a similar purpose, in order to avoid conflict of interests or duplicate work. We encourage collaboration and data sharing for the purpose of the monitoring of the eruption and for research applications. <strong>Data naming convention:</strong> faf_YYYYMMDD_hhmmss_hhmmss_*align.tif: DEM obtained from the processing, co-registered to the reference pre-eruption DEM. faf_YYYYMMDD_hhmmss_hhmmss_*align_diff.tif: Difference of elevation between the Pléiades DEM and the pre-eruption DEM. faf_YYYYMMDD_hhmm.gpkg: Polygon containing the lava outlines, extracted from the Pléiades orthoimage and the map of elevation difference. 0_faf_YYYYMMDD_hhmmss_hhmmss_*fig.png: A figure showing the latest map of elevation difference, overlaid with a hillshade of the latest Pléiades DEM and the latest lava outlines, result of the processing of the Pléiades stereoimages. The figure was created using the tool imviewer.py from the GitHub repository https://github.com/dshean/imview (Shean et al., 2016). <strong>Data Specifications:</strong> 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. <strong>Acknowledgements</strong>: Pléiades images were provided under the CIEST² initiative (CIEST² is part of ForM@Ter (https://en.poleterresolide.fr/) (image Pléiades©CNES2023, distribution AIRBUS DS) <strong>Dataset Attribution</strong>: This dataset is licensed under a Creative Commons CC BY-NC 4.0 International License (Attribution-NonCommercial). <strong>Citation:</strong> Please cite this repository as described below: Joaquin M.C. Belart, Virginie Pinel, Etienne Berthier, &amp; Sydney R. Gunnarson. (2023). Digital Elevation Models (DEMs) and lava outlines from the Litla-Hrútur eruption, Iceland, July 2023 (0.2) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.8144282**引言：** 2023年7月10日16时40分，冰岛雷克雅内斯半岛利特吕特山（Litla-Hrútur）附近发生火山喷发。作为应急响应的一部分，法国CIEST²倡议启动（Gouhier等人，2022）。倡议启动后，研究人员即规划并调度普莱亚德（Pléiades）立体影像，以快速获取研究区域内的影像数据。影像获取并交付后，将按照下文所述方法进行处理。本仓库存储了近实时生成的数字高程模型（Digital Elevation Model, DEM）、与喷发前DEM对比得到的差分图，以及从差分图和正射影像中数字化提取的熔岩轮廓线。本仓库目前仍在完善中，将在普莱亚德立体影像获取周期内持续更新。 **方法：** 普莱亚德立体影像采用艾姆斯立体管线（Ames StereoPipeline, ASP，Shean等人，2016；详见仓库内ASP分支）进行处理，生成了地面采样距离（Ground Sample Distance, GSD）为2×2米的DEM，以及GSD为0.5×0.5米的正射影像。本次处理仅以立体影像及其定向信息——即有理多项式系数（Rational Polynomial Coefficients, RPCs）——作为输入。parallel_stereo程序例程可完成立体影像匹配所需的全部步骤，生成点云；随后通过point2dem程序例程对点云进行插值处理。除默认参数外，本次生成DEM所用的parallel_stereo参数为标准参数外加以下配置：--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。DEM生成后，为对齐喷发前DEM与普莱亚德DEM并最小化二者的位置偏差，我们开展了DEM共配准处理。本次共配准采用Nuth与Kääb（2011）提出的方法，并借助David Shean开发的共配准程序例程（https://github.com/dshean/demcoreg，Shean等人，2016）实现。该共配准流程包含对普莱亚德DEM的水平、垂直偏移校正，以及平面倾斜校正。将DEM共配准得到的水平偏移量同样应用于普莱亚德正射影像。本研究所用的喷发前DEM为冰岛国家土地测量局发布的IslandsDEMv1。熔岩轮廓线通过对配准后的普莱亚德正射影像进行手动数字化提取得到，相关熔岩轮廓线以地理包（GeoPackage）格式存储于本仓库的"GPKG"分支中。目前，冰岛大学地球科学研究所（Jarðvisindustofnun Háskoli Íslands）正采用Pedersen等人（2022）所述方法，借助普莱亚德影像的处理结果估算熔岩体积与喷发速率。若您计划将本数据集用于同类用途，请与作者取得联系，以避免利益冲突或重复研究。我们鼓励为火山喷发监测与科研应用开展合作与数据共享。 **数据命名规则：** faf_YYYYMMDD_hhmmss_hhmmss_*align.tif：经处理得到的、已与参考喷发前DEM完成共配准的DEM文件。 faf_YYYYMMDD_hhmmss_hhmmss_*align_diff.tif：普莱亚德DEM与喷发前DEM的高程差分图。 faf_YYYYMMDD_hhmm.gpkg：包含熔岩轮廓线的矢量多边形文件，从普莱亚德正射影像与高程差分图中提取得到。 0_faf_YYYYMMDD_hhmmss_hhmmss_*fig.png：展示最新高程差分图的配图，叠加了最新普莱亚德DEM的晕渲图与最新熔岩轮廓线，为普莱亚德立体影像处理的结果。该配图采用GitHub仓库https://github.com/dshean/imview（Shean等人，2016）中的imviewer.py工具生成。 **数据规格：** 制图投影：ISN93 / 兰伯特1993坐标系（EPSG:3057，https://epsg.io/3057） 高程基准：基于GRS80椭球体（WGS84）的米级高程值 栅格数据格式：GeoTIFF 栅格压缩方式：LZW 矢量数据格式：地理包（GeoPackage，https://www.geopackage.org/） 本数据集仅包含DEM文件，原因在于普莱亚德正射影像仅可授权使用。若需获取该影像的相关信息，请与作者联系。 **致谢：** 普莱亚德影像由CIEST²倡议提供（CIEST²隶属于ForM@Ter项目（https://en.poleterresolide.fr/）；普莱亚德影像©法国国家空间研究中心2023，发行方：空客防务与航天公司） **数据集归属：** 本数据集采用知识共享署名-非商业性使用4.0国际许可协议（Creative Commons CC BY-NC 4.0 International License）进行授权。 **引用方式：** 请按照以下方式引用本仓库： Joaquin M.C. Belart、Virginie Pinel、Etienne Berthier 与 Sydney R. Gunnarson. (2023). 冰岛2023年7月利特吕特山喷发的数字高程模型与熔岩轮廓线（0.2版本）[数据集]. Zenodo. https://doi.org/10.5281/zenodo.8144282