GIS Features of the Geospatial Fabric for National Hydrologic Modeling

The Geopspatial Fabric provides a consistent, documented, and topologically connected set of spatial features that create an abstracted stream/basin network of features useful for hydrologic modeling.The GIS vector features contained in this Geospatial Fabric (GF) data set cover the lower 48 U.S. states, Hawaii, and Puerto Rico. Four GIS feature classes are provided for each Region: 1) the Region outline ("one"), 2) Points of Interest ("POIs"), 3) a routing network ("nsegment"), and 4) Hydrologic Response Units ("nhru"). A graphic showing the boundaries for all Regions is provided at http://dx.doi.org/doi:10.5066/F7542KMD. These Regions are identical to those used to organize the NHDPlus v.1 dataset (US EPA and US Geological Survey, 2005). Although the GF Feature data set has been derived from NHDPlus v.1, it is an entirely new data set that has been designed to generically support regional and national scale applications of hydrologic models. Definition of each type of feature class and its derivation is provided within the <dataqual><lineage> section of this metadata document. The first <procstep> entry in that section provides an overview of the delineation process, with each subsequent <procstep> corresponding to one of the four types of feature. These <procstep> entries describe the derivation of feature types in the order in which they are created. Minimal attribution (feature size, location, and routing connectivity) is provided for the feature classes within the GF Feature data set. More extensive feature attribution is published separately as individual tables of attributes(for example, http://dx.doi.org/doi:10.5066/F7RX9937) or via entire configurations of tables engineered to satisfy particular watershed models (for example, http://dx.doi.org/doi:10.5066/F7WM1BF7).地理空间框架（Geospatial Fabric, GF）提供了一套统一、可溯源且拓扑连通的空间要素集，可构建抽象化的河道/流域网络要素，适用于水文模拟工作。本地理空间框架数据集包含的GIS矢量要素覆盖美国本土48州、夏威夷州及波多黎各。每个区域均提供四类GIS要素类：1）区域轮廓（"one"）；2）兴趣点（Points of Interest, POIs）；3）汇流网络（"nsegment"）；4）水文响应单元（Hydrologic Response Units, HRUs）。可通过链接http://dx.doi.org/doi:10.5066/F7542KMD 获取展示所有区域边界的图示。本数据集所用的区域划分与NHDPlus v.1数据集（美国环境保护署与美国地质调查局，2005年）完全一致。尽管本GF要素数据集源自NHDPlus v.1，但它是一套全新的数据集，旨在通用化支持区域及国家级尺度的水文模型应用。本元数据文档的<dataqual><lineage>章节中，已详细说明各类要素类的定义及其衍生流程。该章节的首个<procstep>条目概述了要素勾画流程，后续每个<procstep>条目分别对应四类要素中的一类。此类<procstep>条目将按照要素的生成顺序，逐一说明各类要素的衍生过程。本GF要素数据集的各类要素类仅附带最少属性信息，包括要素尺寸、空间位置及汇流连通性。更完整的要素属性信息已作为独立属性表（例如：http://dx.doi.org/doi:10.5066/F7RX9937）或针对特定流域模型定制的整套属性表（例如：http://dx.doi.org/doi:10.5066/F7WM1BF7）单独发布。