USGS Map service: National Shoreline Change - Offshore Baseline

Beach erosion is a chronic problem along most open-ocean shores of the United States. As coastal populations continue to grow, and community infrastructures are threatened by erosion, there is increased demand for accurate information regarding past and present shoreline changes. There is also need for a comprehensive analysis of shoreline movement that is regionally consistent. To meet these national needs, the USGS National Assessment of Shoreline Change Project has collected and analyzed 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.

This dataset includes a reference baseline used by the Digital Shoreline Analysis System (DSAS) to calculate rate-of-change statistics. This baseline layer serves as the starting point for all transects cast by the DSAS application. The resulting rates of change are available in services with the titles USGS Map service: National Shoreline Change - Long-Term Shoreline Change Rates and USGS Map service: National Shoreline Change - Short-Term Shoreline Change Rates.

To make this shoreline data more accessible to the public and other agencies, the USGS created this web service. This web service was created utilizing ESRI ArcServer. This service meets open geospatial consortium standards.

The geographic information system (GIS) data layers from this web service are cataloged by state for ease of access.

海滩侵蚀是美国多数外洋沿岸长期存在的共性问题。随着沿海人口持续增长，社区基础设施不断遭受侵蚀威胁，社会对能够精准反映岸线历史与当前变化的信息需求愈发迫切，同时也亟需开展区域统一的岸线迁移全面分析。为满足这些国家层面的需求，美国地质调查局（United States Geological Survey，USGS）国家岸线变化评估项目通过整合已有历史岸线数据库中的岸线点位，并生成历史与现代岸线数据，收集并构建了一套完整的数字矢量岸线数据库。

本数据集包含供数字岸线分析系统（Digital Shoreline Analysis System，DSAS）计算变化速率统计值所用的参考基线。该基线图层是DSAS工具生成所有剖面的起始基准。最终得到的岸线变化速率可通过以下两类服务获取："美国地质调查局地图服务：国家岸线变化——长期岸线变化速率"以及"美国地质调查局地图服务：国家岸线变化——短期岸线变化速率"。

为便于公众及其他机构获取此类岸线数据，美国地质调查局开发了本网络服务。该服务基于ESRI ArcServer搭建，符合开放地理空间联盟（Open Geospatial Consortium）标准。

本网络服务中的地理信息系统（Geographic Information System，GIS）数据图层按州进行分类编目，以提升访问便捷性。