NORCAL2002 - Vectorized Shoreline of Northern California Derived from 2002 Lidar Source Data

There are critical needs for a nationwide compilation of reliable shoreline data. To meet these needs, the U.S. Geological Survey (USGS) has produced a comprehensive database of digital vector shorelines by compiling shoreline positions from pre-existing historical shoreline databases and by generating historical and modern shoreline data. Shorelines are compiled by state and generally correspond to one of four time periods: 1800s, 1920s-1930s, 1970s, and 1998-2002. Each shoreline may represent a compilation of data from one or more sources for one or more dates provided by one or more agencies. Details regarding source are provided in the 'Data Quality Information' section of this metadata report. Shoreline vectors derived from historic sources (first three time periods) represent the high water line at the time of the survey, whereas modern shorelines (final time period) represent the mean high water line.

全美范围内亟需构建可靠的海岸线数据集合集。为满足这一需求，美国地质调查局（U.S. Geological Survey, USGS）通过整合既有历史海岸线数据库中的海岸线点位，并生成历史与现代海岸线数据，构建了一套全面的数字化矢量海岸线数据库。海岸线数据按州域进行整合，且通常对应以下四个时间段之一：19世纪、1920年代至1930年代、1970年代，以及1998年至2002年。每条海岸线数据均可代表由一个或多个机构提供的、对应一个或多个观测日期的单一组或多组数据源的整合成果。有关数据源的详细信息，请参见本元数据报告的"数据质量信息"章节。源自历史数据源（前三个时间段）的海岸线矢量代表勘测时的高潮线，而现代海岸线（最后一个时间段）则代表平均高潮线。