Digital surface model and orthomosaic of the Chã das Caldeiras lava fields (Fogo Island, Cape Verde, December 2016)

Fogo in the Cape Verde archipelago off Western Africa is one of the most prominent and active ocean island volcanoes on Earth, posing an important hazard to both local populations and at a regional level. The last eruption took place between 23 November 2014 and 8 February 2015 in the Chã das Caldeiras area at an elevation close to 1,800 m above sea level The eruptive episode gave origin to extensive lava flows that almost fully destroyed the settlements of Bangaeira, Portela and Ilhéu de Losna. In December 2016 a survey of the Chã das Caldeiras area was conducted using a fixed-wing unmanned aerial vehicle and RTK GNSS, with the objective of improving the mapping accuracy derived from satellite platforms. The main result is an ultra-high resolution 3D point cloud with a Root Mean Square Error of 0.08 m in X, 0.11 m in Y and 0.12 m in Z, which provides unprecedented accuracy. The survey covers an area of 23. 9 km² and used 2909 calibrated images with an average ground sampling distance of 7.2 cm. The dataset includes the field survey data (aerial images, ground control points and checkpoints), the densified point cloud, the digital surface models and orthomosaics with 10 and 25 cm resolution, as well as the elevation contours at 50 cm interval. The delineation of the 2014-15 lava flows shows an area of 4.53 km² by lava, which is smaller but more accurate than the previous estimates from 4.8 to 4.97 km². The difference in the calculated area, when compared to previously reported values, is due to a more detailed mapping of flow geometry and the exclusion of the areas corresponding to kīpukas. Our study provides an ultra high-resolution dataset of the areas affected by Fogo’s latest eruption – crucial for local planning – and provides a case study to determine the advantages of ultra high-resolution UAV surveys in disaster-prone areas. The details on surveying and processing are described in the manuscript "Very high-resolution terrain surveys of the Chã das Caldeiras lava fields (Fogo Island, Cape Verde) submitted to the journal Earth System Science Data (preprint: https://doi.org/10.5194/essd-2020-289). Please cite the full paper when using the data, This data set contains the following files:<br> - cha_caldeiras_3d_mesh.fbx: 3D mesh in fbx format.<br> - cha_caldeiras_contours_50cm.zip: Compressed shapefile (shp) and auxiliary files. Contour lines of the Chã das Caldeiras in December 2016 with 50 cm equidistance, interpolated from the digital surface model. CRS: ESPG 32626 - WGS 84 / UTM Zone 26N, elevation: ellipsoidal ITRF2014 (WGS84).<br> - cha_caldeiras_dsm_10cm_v2.zip: Compressed Geotiff file. Digital surface model of the Chã das Caldeiras in December 2016 with 10 cm resolution. CRS: ESPG 32626 - WGS 84 / UTM Zone 26N, elevation: ellipsoidal ITRF2014 (WGS84).<br> - cha_caldeiras_dsm_25cm_v2.zip: Compressed Geotiff file. Digital surface model of the Chã das Caldeiras in December 2016 with 25 cm resolution. CRS: ESPG 32626 - WGS 84 / UTM Zone 26N, elevation: ellipsoidal ITRF2014 (WGS84).<br> - cha_caldeiras_checkpoints.zip: Compressed shapefile (shp) and auxiliary files. Coordinates of the ground control points not included in the modelling and used as check points for accuracy assessment. CRS: ESPG 32626 - WGS 84 / UTM Zone 26N.<br> - cha_caldeiras_densified_point_cloud.zip: Compressed densified point cloud file (las). CRS: ESPG 32626 - WGS 84 / UTM Zone 26N.<br> - cha_caldeiras_error_assessment_areas_v2.zip: Compressed shapefile (shp) and auxiliary files. Areas with errors in the point cloud obtained by visual analysis. 1. Low accuracy, 2. Moderate accuracy. CRS: ESPG 32626 - WGS 84 / UTM Zone 26N.<br> - cha_caldeiras_gcps.zip: Compressed shapefile (shp) and auxiliary files. Coordinates of the ground control points used to georeferenced the model. CRS: ESPG 32626 - WGS 84 / UTM Zone 26N.<br> - cha_caldeiras_ortho_10cm_v2.zip: Compressed Geotiff file. Orthomosaic RGB of the Chã das Caldeiras in December 2016 with 10 cm resolution. CRS: ESPG 32626 - WGS 84 / UTM Zone 26N, elevation: ellipsoidal ITRF2014 (WGS84).<br> - cha_caldeiras_ortho_25cm_v2.tif: Orthomosaic RGB of the Chã das Caldeiras in December 2016 with 25 cm resolution. CRS: ESPG 32626 - WGS 84 / UTM Zone 26N.<br> - cha_caldeiras_pix4d_report.pdf: Report of the processing of the aerial imagery in PIX4D.<br> - ebee_fogo_projetos.zip: Compressed PIX4D project files (p4d) with the full aerial imagery of the surveys in Chã das Caldeiras.<br> - lava-2014-15.zip: Compressed shapefile (shp) and auxiliary files. Lava flows of the eruption of 2014-15 digitised from the original 10 cm resolution orthomosaic. CRS: ESPG 32626 - WGS 84 / UTM Zone 26N.位于西非外海佛得角群岛的福戈岛（Fogo），是地球上最显著且活动最为频繁的海洋岛火山之一，对当地居民及区域范围内均构成了严重的灾害威胁。其最近一次喷发发生于2014年11月23日至2015年2月8日期间，喷发地点位于卡尔代拉斯平原（Chã das Caldeiras）区域，海拔接近1800米。此次喷发形成了大范围的熔岩流，几乎完全摧毁了班盖拉（Bangaeira）、波特拉（Portela）与洛斯纳岛（Ilhéu de Losna）三处定居点。 2016年12月，研究团队采用固定翼无人机（fixed-wing unmanned aerial vehicle）与实时动态全球导航卫星系统（RTK GNSS, Real-Time Kinematic Global Navigation Satellite System）对卡尔代拉斯平原区域开展了勘测，旨在提升基于卫星平台获取的测绘精度。本次勘测的核心成果为一套超高分辨率三维点云，其X轴方向均方根误差为0.08米，Y轴为0.11米，Z轴为0.12米，精度达到了前所未有的水平。此次勘测覆盖面积达23.9平方千米，共使用2909张经过校准的影像，平均地面采样距离为7.2厘米。 本数据集涵盖野外勘测数据（航空影像、地面控制点与检查点）、加密点云、分辨率分别为10厘米与25厘米的数字表面模型（digital surface model）与正射影像镶嵌图（orthomosaic），以及间隔为50厘米的高程等高线。通过对2014-2015年熔岩流的勾绘，测得其覆盖面积为4.53平方千米，相较于此前报道的4.8至4.97平方千米的估算值，面积更小但精度更高。二者面积计算结果存在差异的原因在于本次研究对熔岩流几何形态开展了更为精细的测绘，并剔除了对应于 kipuka（熔岩包围的残留地块）的区域。 本研究提供了福戈岛最新喷发影响区域的超高分辨率数据集，这对当地规划工作至关重要；同时也为探究超高分辨率无人机勘测在灾害频发区域的应用优势提供了典型案例。关于勘测与数据处理的详细内容已发表于论文"Very high-resolution terrain surveys of the Chã das Caldeiras lava fields (Fogo Island, Cape Verde)"，该文已提交至《Earth System Science Data》期刊（预印本链接：https://doi.org/10.5194/essd-2020-289）。使用本数据集时请引用该完整论文。 本数据集包含以下文件：<br>- cha_caldeiras_3d_mesh.fbx：FBX格式三维网格模型。<br>- cha_caldeiras_contours_50cm.zip：压缩格式形状文件（shp）及辅助文件，包含2016年12月卡尔代拉斯平原的高程等高线，间隔为50厘米，由数字表面模型插值生成。坐标参考系：ESPG 32626 - WGS 84 / UTM Zone 26N，高程采用ITRF2014椭球高（WGS84）。<br>- cha_caldeiras_dsm_10cm_v2.zip：压缩格式GeoTIFF文件，为2016年12月卡尔代拉斯平原的10厘米分辨率数字表面模型。坐标参考系：ESPG 32626 - WGS 84 / UTM Zone 26N，高程采用ITRF2014椭球高（WGS84）。<br>- cha_caldeiras_dsm_25cm_v2.zip：压缩格式GeoTIFF文件，为2016年12月卡尔代拉斯平原的25厘米分辨率数字表面模型。坐标参考系：ESPG 32626 - WGS 84 / UTM Zone 26N，高程采用ITRF2014椭球高（WGS84）。<br>- cha_caldeiras_checkpoints.zip：压缩格式形状文件（shp）及辅助文件，包含未参与建模、仅用于精度评估的地面检查点坐标。坐标参考系：ESPG 32626 - WGS 84 / UTM Zone 26N。<br>- cha_caldeiras_densified_point_cloud.zip：压缩格式加密点云文件（LAS格式）。坐标参考系：ESPG 32626 - WGS 84 / UTM Zone 26N。<br>- cha_caldeiras_error_assessment_areas_v2.zip：压缩格式形状文件（shp）及辅助文件，包含通过目视分析得到的点云误差区域，其中1代表低精度区域，2代表中精度区域。坐标参考系：ESPG 32626 - WGS 84 / UTM Zone 26N。<br>- cha_caldeiras_gcps.zip：压缩格式形状文件（shp）及辅助文件，包含用于对模型进行地理配准的地面控制点坐标。坐标参考系：ESPG 32626 - WGS 84 / UTM Zone 26N。<br>- cha_caldeiras_ortho_10cm_v2.zip：压缩格式GeoTIFF文件，为2016年12月卡尔代拉斯平原的10厘米分辨率RGB正射影像镶嵌图。坐标参考系：ESPG 32626 - WGS 84 / UTM Zone 26N，高程采用ITRF2014椭球高（WGS84）。<br>- cha_caldeiras_ortho_25cm_v2.tif：2016年12月卡尔代拉斯平原的25厘米分辨率RGB正射影像镶嵌图。坐标参考系：ESPG 32626 - WGS 84 / UTM Zone 26N。<br>- cha_caldeiras_pix4d_report.pdf：PIX4D航空影像处理报告。<br>- ebee_fogo_projetos.zip：压缩格式PIX4D项目文件（P4D格式），包含卡尔代拉斯平原勘测的全部航空影像数据。<br>- lava-2014-15.zip：压缩格式形状文件（shp）及辅助文件，包含从原始10厘米分辨率正射影像镶嵌图中数字化得到的2014-2015年喷发熔岩流。坐标参考系：ESPG 32626 - WGS 84 / UTM Zone 26N。