Shorelines from 1949 to 2015 for the northwest coast of Alaska (Cape Prince of Wales to Kotlik River) used in shoreline change analysis

Horizontal positional accuracy for this dataset is composed of three contributing factors: georeferencing error, digitization error, and the water line position uncertainty. The georeferencing error was estimated by identifying the same features in imagery from each time period (1950s, 1980s, and 2015), measuring the horizontal distance between the same feature in different imagery datasets, then calculating the RMSE for each imagery processing region for the 1950s and 1980s datasets. These values ranged from 3.12 to 3.86 meters for 1950s and 2.42 to 3.89 meters for the 1980s. The georeferencing error for all 2015 imagery was reported by contractor (Fairbanks Fodar) to be 0.3 meters. The digitization error is the variability in the digitized location of the vector shoreline. The digitization error was determined to be 3 meters for the 1950s imagery, 3 meters for the 1980s imagery, and 2 meters for the 2015 imagery. The uncertainty of the position of the water line at the time of imagery capture was calculated by dividing the minimum and maximum water level deviations from mean high water, using the NOAA Tide Predictions based on the tidal stations at Unalakleet (9468333) and Nome (9468756), by the estimated shoreface slope (1:20). These three components were added in quadrature. The resulting horizontal positional accuracy ranged from 2.13 meters to 8.93 meters.