Copernicus Digital Elevation Model (DEM) for Europe at 100 meter resolution (EU-LAEA) derived from Copernicus Global 30 meter DEM dataset

Overview: The Copernicus DEM is a Digital Surface Model (DSM) which represents the surface of the Earth including buildings, infrastructure and vegetation. The original GLO-30 provides worldwide coverage at 30 meters (refers to 10 arc seconds). Note that ocean areas do not have tiles, there one can assume height values equal to zero. Data is provided as Cloud Optimized GeoTIFFs. Note that the vertical unit for measurement of elevation height is meters. The Copernicus DEM for Europe at 100 meter resolution (EU-LAEA projection) in COG format has been derived from the Copernicus DEM GLO-30, mirrored on Open Data on AWS, dataset managed by Sinergise (https://registry.opendata.aws/copernicus-dem/). Processing steps: The original Copernicus GLO-30 DEM contains a relevant percentage of tiles with non-square pixels. We created a mosaic map in VRT format and defined within the VRT file the rule to apply cubic resampling while reading the data, i.e. importing them into GRASS GIS for further processing. We chose cubic instead of bilinear resampling since the height-width ratio of non-square pixels is up to 1:5. Hence, artefacts between adjacent tiles in rugged terrain could be minimized: gdalbuildvrt -input_file_list list_geotiffs_MOOD.csv -r cubic -tr 0.000277777777777778 0.000277777777777778 Copernicus_DSM_30m_MOOD.vrt In order to reproject the data to EU-LAEA projection while reducing the spatial resolution to 100 m, bilinear resampling was performed in GRASS GIS (using r.proj and the pixel values were scaled with 1000 (storing the pixels as Integer values) for data volume reduction. In addition, a hillshade raster map was derived from the resampled elevation map (using r.relief, GRASS GIS). Eventually, we exported the elevation and hillshade raster maps in Cloud Optimized GeoTIFF (COG) format, along with SLD and QML style files. Projection + EPSG code: ETRS89-extended / LAEA Europe (EPSG: 3035) Spatial extent: north: 6874000 south: -485000 west: 869000 east: 8712000 Spatial resolution: 100 m Pixel values: meters * 1000 (scaled to Integer; example: value 23220 = 23.220 m a.s.l.) Software used: GDAL 3.2.2 and GRASS GIS 8.0.0 (r.proj; r.relief) Original dataset license: https://spacedata.copernicus.eu/documents/20126/0/CSCDA_ESA_Mission-specific+Annex.pdf Processed by: mundialis GmbH & Co. KG, Germany (https://www.mundialis.de/)

概览：哥白尼数字高程模型（Copernicus DEM）是一款数字表面模型（Digital Surface Model，DSM），可表征包含建筑物、基础设施与植被在内的地球地表形态。原始GLO-30数据集具备全球覆盖范围，分辨率为30米（对应10角秒）。需注意，海洋区域无对应瓦片，默认其高程值为0。数据以云优化地理TIFF（Cloud Optimized GeoTIFF，COG）格式提供，高程测量的垂直单位为米。
针对欧洲区域的100米分辨率哥白尼DEM（采用EU-LAEA投影），其数据源自哥白尼DEM GLO-30，镜像存储于亚马逊云开放数据（Open Data on AWS）平台，该数据集由Sinergise管理（https://registry.opendata.aws/copernicus-dem/）。

处理流程：原始哥白尼GLO-30 DEM存在相当比例的非方形像素瓦片。我们首先创建了虚拟栅格数据集（Virtual Raster Dataset，VRT）格式的镶嵌图，并在VRT文件中定义了读取数据时采用三次重采样的规则，随后将数据导入GRASS GIS进行后续处理。之所以选择三次重采样而非双线性重采样，是因为非方形像素的高宽比最高可达1:5，此举可最大程度减少崎岖地形中相邻瓦片间的伪影。具体处理命令如下：
`gdalbuildvrt -input_file_list list_geotiffs_MOOD.csv -r cubic -tr 0.000277777777777778 0.000277777777777778 Copernicus_DSM_30m_MOOD.vrt`
为将数据重投影至EU-LAEA投影并将空间分辨率降至100米，我们在GRASS GIS中执行了双线性重采样（使用r.proj工具），并将像素值缩放1000倍（将像素存储为整型数值）以缩减数据体量。此外，我们基于重采样后的高程图生成了晕渲栅格图（使用GRASS GIS的r.relief工具）。最终，我们将高程与晕渲栅格图导出为云优化地理TIFF（COG）格式，同时附带SLD与QML样式文件。

投影及EPSG代码：ETRS89扩展版 / 欧洲LAEA投影（EPSG: 3035）
空间范围：北：6874000；南：-485000；西：869000；东：8712000
空间分辨率：100米
像素值说明：像素值为高程值（米）缩放1000倍后的整型数值；示例：数值23220对应海拔23.220米（相对于平均海平面）
所用软件：GDAL 3.2.2与GRASS GIS 8.0.0（包含r.proj、r.relief工具）
原始数据集许可：https://spacedata.copernicus.eu/documents/20126/0/CSCDA_ESA_Mission-specific+Annex.pdf
处理方：德国mundialis GmbH & Co. KG（https://www.mundialis.de/）