For additional information describing the data the reader is referred to the dictionary document (http://coastalgeospatial.noaa.gov/gis_files/shoreline/shoreline_data_dictionary.html).
The data supplied here are a compilation of information collected from some 270+ current or pre-release National Ocean Service Navigation Charts. In compiling this product we made no attempt to ascertain the congruency between the charted data, and the real world. Our objective was to simply capture the representative coastline as provided to us via the NOS Chart. Every effort was made to capture the shoreline on these charts as faithfully as our skills and technology allowed, and there is every indication that we were successful to this end. However, in doing so, we automatically conveyed the character (all aspects, both good and bad) of those data to our digital product. A character which may or may not be in agreement with the real world. Because of this, the user is advised to exercise caution in making any assumptions about the fallibility, or infallibility, of the spatial information supplied here; especially when circumstances warrant a high degree of absolute positional accuracy.
A complete description of the process steps is available in the Procedures document file (http://coastalgeospatial.noaa.gov/gis_files/shoreline/data/docs/procs.txt).
Estimation arcs are used for two purposes: first, to fill in gaps in the shoreline as depicted on the chart (other than those areas which would be considered truncations), and secondly, to identify captured (digitized) shoreline arcs which have been modified in some way either for error rectification or edge matching adjustments. The span of these arcs range from five meters to several tens of meters in length. In the first case, estimator arcs attempt to simulate or mimic the actual shape or course of the coastline in the missing area. Insertion of these arcs into the data is done using heads up methods with the appropriate navigational chart(s) as a guide. In the second case, an existing arcs terminal to node is moved from its original captured location to a position where it can be connected to the concomitant arc's node from an adjacent chart. Additional vertices may then be added to replicate the course of the original information. Modification of existing arcs was carried out such that disruption of the information was minimized. Estimate arcs are identified in the data by the codes: S_SOURCE = 4, S_ARC_CODE = 5.
If the accuracy of the data could not be assessed and thus categorized into one of the five qualitative integrity classes, the arc was classified with an integrity of unknown. Most of the arcs grouped into the unknown category were those captured early in the project. During that time source materials (primarily master compilations and X-drawings) were assumed to be of equal stability and accuracy. This was not, however, the case. Once this disparity was recognized, source tracking procedures were implemented and the integrity of the captured information, based on the stability and clarity of the source media was tracked and assessed.
1. East Coast -U.S./Canada Border at the St. Croix River to the southern tip of the Florida Peninsula (including the Keys)
2. Gulf of Mexico Coast -Southern tip of the Florida Peninsula (no Keys) to the U.S./Mexico Border at Brownsville, Texas.
3. West Coast -U.S./Mexico Border at Baja to U.S./Canada Border at the Straits of Juan DeFuca.
4. Great Lakes -All five lakes, in their entirety, including the connecting waterways (except the St. Lawrence River/Seaway).
For practical reasons the sections were further divided into three or more components:
Atlantic Coastal Section:
ec80_01 - St. Mary's Inlet Florida to Little River Inlet South Carolina;
ec80_02 - Little River Inlet South Carolina to Cape Henry, Virginia;
ec80_03 - Chesapeake Bay;
ec80_04 - Chincoteague Inlet Virginia to Block Island Sound Rhode Island;
ec80_05 - Point Judith to St. Croix River;
ec80_06 - St. Mary's River, Florida to Florida Bay (including the Florida Keys.);
Gulf Coastal Section:
gc80_01 - Padre Island TX to Bayou Choupique, LA;
gc80_02 - Lake Calcasieu, LA to Atchafalaya Bay, LA;
gc80_03 - Point Au Fer, LA to Barataria Pass, LA;
gc80_04 - Grand Terre Island, LA to Gulfport, MS, incl. the Chandeleurs Islands;
gc80_05 - Biloxi River, MS to Chassahowitza Reefs, FL;
gc80_06 - Chassahowitza Reefs, FL to Flamingo, FL;
Pacific Coastal Section:
wc80_01 - Semiahoo Bay, WA to Yaquina Head, OR;
wc80_02 - Alsea Bay, OR to Point Sur, CA;
wc80_03 - Point Sur, CA to U.S./Mexico Border;
Great Lakes Section:
gl80_01 - Lake Superior;
gl80_02 - Lake Michigan incl. Lake Winnebago, WI;
gl80_03 - Lake Huron incl. North Channel, and Georgian Bay;
gl80_04 - Lake Erie incl. Detroit, St. Clair, and Niagara Rivers, and Lake St. Clair;
gl80_05 - Lake Ontario incl. St. Lawrence River to Ogdensburg, NY.