TESTING THE ACCURACY OF HEADS-UP-DIGITIZING AND ESTUARINE SHORELINE CHARACTERIZATION, OCRACOKE, NC

This project tested the use of heads-up-digitizing to delineate and characterize the estuarine shoreline and coastal structures. This was accomplished by digitizing aerial photography in ArcGIS and in-situ mapping of estuarine shoreline segments and coastal structures of Ocracoke Island, NC. East Carolina University scientists are working with the NC Division of Coastal Management (NCDCM) to digitize the estuarine shoreline of NC. The digitizing methodology was established by a panel of NC researchers and managers (ArcGIS users), and finalized by the NCDCM. To test the accuracy of digitized shorelines, sections of Ocracoke Island were surveyed using a Trimble 5800 Real-time Kinematic Global Positioning System. While datasets are not concurrent, the temporal offset was minimal (about 2 years). ArcGIS analysis was used to address potential error in the method and provide estimates of shoreline erosion between aerial-photograph collection and field-based mapping. In order to test the shoreline characterization by digitization, a boat with GPS was used to survey the shoreline while mapping and photographing shoreline features. These data were then compared to the heads-up digitization results. Physically mapped shoreline was found to be relatively consistent with the heads-up-digitized shoreline. However, many small structures were apparently missed in the digitization of aerial photographs.