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<p>The National Hydrography Dataset (NHD) is a feature-based database that interconnects and uniquely identifies the stream segments or reaches that make up the nation's surface water drainage system. NHD data was originally developed at 1:100,000 scale and exists at that scale for the whole country. High resolution NHD adds detail to the original 1:100,000-scale NHD. (Data for Alaska, Puerto Rico and the Virgin Islands was developed at high-resolution, not 1:100,000 scale.) Like the 1:100,000-scale NHD, high resolution NHD contains reach codes for networked features and isolated lakes, flow direction, names, stream level, and centerline representations for areal water bodies. Reaches are also defined to represent waterbodies and the approximate shorelines of the Great Lakes, the Atlantic and Pacific Oceans and the Gulf of Mexico. The NHD also incorporates the National Spatial Data Infrastructure framework criteria set out by the Federal Geographic Data Committee.</p>

国家水文数据集（National Hydrography Dataset）是一款基于要素的数据库，可对构成该国地表排水系统的河流河段进行互联互通与唯一标识。NHD数据最初以1:10万比例尺开发，全国范围内均采用该比例尺数据。高分辨率NHD则为原始1:10万比例尺NHD补充了细节信息。（阿拉斯加、波多黎各及美属维尔京群岛的数据采用高分辨率模式开发，未采用1:10万比例尺。）与1:10万比例尺NHD一致，高分辨率NHD包含网络化要素与孤立湖泊的河段编码、水流流向、河流名称、河流等级，以及面状水体的中心线表达形式。河段的定义还可用于表征各类水体，以及五大湖、大西洋、太平洋与墨西哥湾的近似岸线。NHD同时纳入了联邦地理数据委员会（Federal Geographic Data Committee）制定的国家空间数据基础设施（National Spatial Data Infrastructure）框架准则。