The data sets that comprise this data base include the following: elevation, geology, geomorphology, sea-level trends, horizontal shoreline displacement (erosion/accretion), tidal ranges, and wave heights. The original data used in developing the data variables included in this NDP were obtained in a variety of scales and formats (e.g., as polygon, line, or point data). Therefore, the methods used to enter the data into the 0.25° grid cells and 1:2,000,000 digitized line segments vary by data set. The variable descriptions used in this report were extracted from annual reports submitted in April 1988, November 1988, April 1991 [Gornitz 1988a, 1988b, 1991; Gornitz and White (Beaty) 1991]; and personal correspondence between Gornitz and Beaty in 1995 and 1996. The following subsections provide a brief description of the data sources and the classification methods used in compiling each data set.