NOAA Shoreline Website

NOAA Composite Shoreline

Purpose and Potential Applications: This data set was primarily created for high-resolution cartographic representation. Other potential applications include boundary determination.

Originator(s): National Oceanic and Atmospheric Administration (NOAA) Office for Coastal Management

Abstract: The NOAA Office for Coastal Management’s composite shoreline is a high-resolution vector shoreline based on a multi-temporal collection of NOAA shoreline manuscripts (T-sheets). It is critical that users refer to the source and date of the shoreline, since some areas of the U.S. are prone to erosion or accretion.

Access: Download NOAA Composite Shoreline

Scale(s): 1:5,000 to 1:20,000

Coverage: Continental U.S. and Hawaii

Source Data: T-sheets, which are special-use planimetric or topographic maps that precisely define the shoreline and alongshore natural and man-made features, such as rocks, bulkheads, jetties, piers, and ramps. Where T-sheets are unavailable, NOAA’s extracted vector shoreline (EVS) was used to compile seamless shoreline coverage.

Spatial Reference: Geographic coordinate system (decimal degrees); Horizontal Datum – North American Datum of 1983 (NAD83)

Tidal Datum: Mean high water (MHW)

Data Format: ESRI shapefile.  Shoreline data is distributed as a nationally seamless line or polygon.

Accuracy: The average accuracy of the measured benchmarks is 3.06 meters (10 feet), and this meets the National Ocean Service (NOS) guidelines for fixed aids to navigation and objects charted as landmarks. This accuracy is stricter than national standards and four times the accuracy of current U.S. Geological Survey 1:24,000-scale topographic maps. Because of this, the original T-sheets can be assumed to also meet NOS guidelines and to be very accurate in their depiction of the shoreline that existed at the time of the surveys.

Process Description: The 13,782 shoreline manuscripts (T-sheets) were scanned and converted to raster format. Raster manuscript scans were saved as .tif or .jpg at 250 or 1200 dpi respectively.

ERDAS IMAGINE software was used for georeferencing. T-sheets were georeferenced in a geographic coordinate system, spheroid Clarke 1866, and North American Datum 1927. Georeferencing was not acceptable, with a total root mean square (RMS) error over 2.00. To confirm proper alignment, ERDAS IMAGINE 8.7 and Terraserver Imagery were used to check for alignment and validity of georeferencing work.

ESRI ArcMap 9.1 was used to vectorize relevant shoreline features present in the shoreline raster files. During the vectorization process, attention to line work accuracy and attribute coding was assured through quality checks by a geographic information system analyst. The final vectors were re-analyzed in ESRI ArcMap 9.2 for quality control.

Once all T-sheets for a state have been vectorized and georeferenced, the individual files are joined together so that all lines are connected through a process known as edge matching. Where gaps exist in the shoreline coverage, EVS data are used to complete the coverage. If multiple T-sheet files exist for a given area, priority is give to the most recent shoreline segment. T-sheets dating to pre-1950 are replaced with extracted vector shoreline data. All files are appended together into a statewide file.