Created from the Cartographic and Geospatial Technology Program's (CGTP) Extracted Vector Shoreline Series, the Merged Extracted Vector Shoreline is a seamless vector shoreline file designed to provide users a topologically clean shoreline file depicting the Mean High Water line for the continental U.S., Hawaii, Alaska, and U.S. territories.

The main purpose of the Charted Vector Shoreline Project is to provide public access to accurate and current coastline and shoreline data. The project targets scales between 1:10,000 and 1:80,000 with emphasis on the larger scales. Using processes and software designed by the Cartographic and Geospatial Technology Programs (CGTP), the vector data are automatically extracted from the NOAA Nautical Charts.

From each chart, Mean High Water and Mean Lower Low Water lines are extracted as vector lines from the binary raster files used in nautical chart production. The resulting vector high and lower low water lines are derived from the legal depictions on nautical charts for the United States. The resulting line files are checked for accuracy and converted from paper-charted units to geographic positions and imported to the shape file format used in GIS (Geographic Information Systems) applications.

http://nauticalcharts.noaa.gov/csdl/ctp/cm_vs.htm