Abstract:

The National Oceanic and Atmospheric Administration's (NOAA) Coastal Services Center (CSC) has recently begun a project with AmeriCorps to vectorize the shoreline from NOAA raster topographic sheets (T-sheets). The final product will be a high-resolution vector shoreline coverage of the Southeastern United States produced from source material with scales ranging from 1:5,000 to 1:20,000. T-sheets are a byproduct of NOAA chart production and are captured using highly accurate, tide-controlled photography. The vector shoreline will be used in coastal zone and ocean GIS applications.

Introduction: The coastal resource management community has a need for a high-resolution vector shoreline for use in geographic information system (GIS) applications that include coastal hazards mitigation, ocean governance, permitting, beach nourishment, oil spill response, and coastal planning. Currently, the most comprehensive national vector shoreline database has a median scale of 1:70,000. This shoreline file was digitized from NOAA's Nautical Charts ranging in scales between 1:50,000 to 1:100,000. Though this shoreline file is of a nationwide scope (conterminous 48 states) it lacks the high resolution needed in support of many of the site-specific decisions that must be made by local communities. This paper outlines the process by which the CSC, in conjunction with AmeriCorps, is creating a high-resolution vector shoreline coverage for the southeastern U.S.

The high-resolution vector shoreline is currently being vectorized from a byproduct, called a topographic survey map or T-sheet, of the NOAA nautical chart production process. The photography that was used to create the charts is the only universal, tide-controlled product that exists for the entire U.S. Approximately 150 T-sheets cover the southeastern states of North Carolina, South Carolina, and Georgia and the scales range from 1:5,000 to 1:20,000. Each stable base plot has been scanned and resides in a .PCX format. Using Environmental Systems Research Institute's (Esri) ArcInfo, the files are converted to a grid format. To facilitate the georeferencing of the grid files, a series of ArcView Avenue scripts were written to create a tic .dbf file; select the control points off the graticule; and pass the necessary files to ArcInfo for processing. The georeferenced files are then ready for processing by the AmeriCorps students.

The National and Community Service's Civilian Corps (AmeriCorps) is a federally-funded program dedicated to promote community service. This vectorization project is within the definition of community service because the shoreline data will be used by national, regional, and local coastal resource managers in the protection of the coast. AmeriCorps volunteers, who range in age from 18 to 24 and have no experience in GIS, come to the CSC computer training lab for five week periods. They receive preparatory training in computer skills, GIS, and coastal zone management issues. After completing the introductory training, they receive in-depth instruction into Esri's ArcScan software. Approximately two days are necessary for this training in order that the Corps members are suitably trained for production. Each student is assigned a raster T-sheet to vectorize.

The vector database design includes aspects of the original photogrammetric nautical chart production. Only the physical features of shoreline, dike, jetty, breakwater, groin, and pier are discernible on the raster image and are coded. This database design also includes attributes for any user defined arc which is important for metadata lineage. The dates of photography, compilation, final review and GIS automation are encoded for every line, as is the scale of the map.

ArcTools is used to facilitate vectorization of the arcs and coding of the attributes. Customized menus and Arc Macro Language programs (AML) were created to streamline the amount of training required for production by novice users. An AML was written for the users to create the hardcopy plots for quality assurance/quality control (QA/QC). Using these procedures, each AmeriCorps student is able to produce, on the average, one digital shoreline coverage each week. This includes time spent training, coding, reviewing, and editing.

CSC staff provide the training and final supervision of the QA/QC process. Edgematching of adjoining digital files and creation of Federal Geographic Data Committee (FGDC)-compliant metadata will also be conducted by CSC staff.

This project between NOAA's CSC and AmeriCorps benefits both partners. The CSC derives the benefit of providing an accurate high-resolution shoreline to the coastal resource management community. The AmeriCorps students gain an invaluable experience of providing community service while gaining the hand-on training with computers, coastal-zone issues, and GIS. The shoreline vectorization project for the Southeast will continue through 1998. Interim products may be made available for selected regions. At the completion of the project, an evaluation will be made as to whether this or other shoreline capture processes should be continued in other regions.