Hydrologic Derivatives for Modeling and Applications (HDMA) Data

The Hydrologic Derivatives for Modeling and Analysis (HDMA) database provides comprehensive and consistent global coverage of raster and vector topographically derived layers. The HDMA includes five raster layers: digital elevation model (DEM) data, flow direction, flow accumulation, slope, and compound topographic index (CTI); and three vector layers: streams, catchment boundaries, and processing units. The coverage of the data is global (-180, 180, -90, 90) with the underlying DEM being a hybrid of three datasets: HydroSHEDS (Hydrological data and maps based on SHuttle Elevation Derivatives at multiple Scales), Global Multi-resolution Terrain Elevation Data 2010 (GMTED2010) and the Shuttle Radar Topography Mission (SRTM). For most of the globe south of 60 North, the raster resolution of the data is 3-arc-seconds, corresponding to the resolution of the SRTM. For the areas North of 60, the resolution is 7.5-arc-seconds (the smallest resolution of the GMTED2010 dataset) except for Greenland, where the resolution is 30-arc-seconds. The streams and catchments are attributed with Pfafstetter codes, based on a hierarchical numbering system, that carry important topological information.

建模与分析用水文导数（Hydrologic Derivatives for Modeling and Analysis, HDMA）数据库提供了覆盖全球的全面且一致的栅格与矢量地形衍生图层。该数据集包含五类栅格图层：数字高程模型（digital elevation model, DEM）数据、流向、流量累积、坡度以及复合地形指数（compound topographic index, CTI）；同时包含三类矢量图层：水系、汇水区边界与处理单元。该数据集的覆盖范围为全球全域（经度-180°至180°，纬度-90°至90°），其基础数字高程模型融合了三类数据集：HydroSHEDS（基于多尺度航天飞机高程导数的水文数据与地图）、全球多分辨率地形高程数据2010（Global Multi-resolution Terrain Elevation Data 2010, GMTED2010）以及航天飞机雷达地形测绘任务（Shuttle Radar Topography Mission, SRTM）。全球北纬60°以南的绝大多数区域，栅格分辨率为3角秒，与SRTM的分辨率一致。北纬60°以北的区域，栅格分辨率为7.5角秒（为GMTED2010数据集的最小分辨率），但格陵兰地区除外，其分辨率为30角秒。水系与汇水区均附带基于层级编号系统的帕夫施泰特编码（Pfafstetter codes），该编码承载了关键的拓扑信息。