Historical Shoreline for New Jersey (1971 to 1978): Vector Digital Data

Imagery was acquired from the NJGIN on an external hard drive as individual image tiles and was opened using ArcGIS 10.3.1. The image tiles for each timeframe (1971-78 and 1977-78) were mosaicked into two mosaic datasets using North American Datum of 1983 state plane for New Jersey Federal Information Processing Standard Zone 2900, in feet (NAD_1983_StatePlane_New_Jersey_FIPS_2900_Feet).

Using the ArcMap 10.3.1 editor toolbar, the foreshore, backshore, mainland and islands were digitized based on a visual assessment of shoreline locations within the imagery, at a scale of 1:1,500. The 1971-78 mosaic imagery was used as the primary source for delineating and digitizing shorelines. If necessary, the 1977-78 mosaic imagery was used to fill in missing areas or justify shoreline positions in areas where it was not apparent in the 1971-77 imagery. The foreshore was digitized using the wet/dry line along the open-ocean facing side of the barrier island as a proxy for mean high water (MHW) shoreline position. The backshore was digitized using the land-water boundary along the estuarine side of the barrier island as a proxy for shoreline position. The mainland was digitized using the land-water boundary between the mainland and estuary as a proxy for shoreline position. Islands were classified as land not connected to the foreshore or backshore of the barrier island or the mainland and were digitized using the land-water boundary as a proxy for shoreline position. For consistency, small islands and creeks were not digitized, since they were not necessary for the shoreline change analysis. In addition, the following fields were added to the shoreline’s attribute table and calculated as necessary: "Shoreline" (Text/25), "Date_" (Text/25), "Year" (Text/10), “Accuracy” (double), and “Notes” (text/254). See the “Entity and Attribute Information” section for additional information.

Dates were not included in the NJGIN imagery so they were acquired from the New Jersey Department of Environmental Protection (NJDEP) via personal communication, as two Excel spreadsheets. Using the NJDEP tidelands grid (available at http://www.state.nj.us/dep/gis/stateshp.html#TIDEGRID) the Excel spreadsheets were joined to it, based on the grid number. The updated grid, with dates, was then used to split the shorelines into their respective grids and a spatial join was used to add the dates from the grid to the shoreline shapefile.

Added keywords section with USGS persistent identifier as theme keyword.