AL1849-1867 - Vectorized Shoreline of Alabama Derived from 1849-1867 Source Data

There are critical needs for a nationwide compilation of reliable shoreline data. To meet these needs, the 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.

全国范围内可靠海岸线数据集的汇编工作存在迫切现实需求。为满足该需求，美国地质调查局（USGS）通过整合现有历史海岸线数据库中的海岸线位置信息，并生成历史与现代海岸线数据，构建了一套完整的数字矢量海岸线综合数据库。海岸线按行政州进行汇编，且通常对应以下四个时间段之一：19世纪、1920年代-1930年代、1970年代以及1998年-2002年。每条海岸线的数据可整合自一个或多个机构提供的、对应单个或多个观测日期的一个或多个数据源。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，代表勘测实施时的高潮线；而现代海岸线（最后一个时间段）则代表平均高潮线。