PART III: DATA REDUCTION 



Data Sources 



54. Forty- two historical NOS and C&GS shoreline surveys and maps, at 

 scales varying from 1:5000 to 1:40,000 and dating from 1849 through 1975, 

 exist for the study area. The earliest surveys (up to around 1927) were 

 "topographic surveys" and were practically all completed by planetable. Since 

 1927, aerial photography and photogrammetric methods (thus photogrammetric 

 surveys) have been used increasingly to provide topographic information along 

 the coast (Shalowitz 1964, p 52). 



55. Eighteen l:24,000-scale U. S. Geological Survey (USGS) quadrangles 

 were selected to be the base maps for this project (Figure 25). They were re- 

 vised by the Cartographic Revision Section of the Photogrammetry Division of 

 NOS with l:24,000-scale color photography, taken on 16 March 1980 at near high 

 water, covering both sides of the barrier island and all of the ocean coast 

 within the project. This procedure is described more fully below. The 

 historical sheets available for each base map, with their scales and dates of 

 survey, are listed in Table 4. A particular sheet may often be listed on more 

 than one base map; each base map usually comprises sheets of varying scales 

 and area limits. 



Shoreline Definition 



56. Topographic surveys, in support of hydrographic surveys, have been 

 compiled by NOS since the early 1800' s. These surveys are the basis for the 

 delineaton of the shoreline on the nautical charts published by the Agency. 

 According to Shalowitz (1964), the authority on the historical significance 

 of early topographic surveys of NOS, "The most important feature on a topo- 

 graphic survey is the high-water line." High-water line (HWL) is a general 

 term; because it is used in this report as the shoreline, it must be defined 

 as actually surveyed through the years by NOS and its predecessors. 



57. About 1840, Ferdinand Hassler, the first Superintendent of the 

 Survey, issued the earliest instructions for topographic work. Those instruc- 

 tions (Volume 17, Coast Survey, Scientific, 1844-1846, handwritten) included 

 the following: 



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