PART III: METHODOLOGY 



45. Procedures used for selection of data sources, shoreline defini- 

 tion, and map production were established by the NOS and were common to all 

 three shoreline reports in this series. The first report (Everts, Battley, 

 and Gibson 1983) clearly outlines methodology used to construct the shoreline 

 change maps. Text in this part of the report covering map-making procedures 

 borrows heavily from Everts, Battley, and Gibson (1983); however, procedures 

 for map analysis are substantially different. 



Data Sources 



46. Thirty-two 1: 24,000-scale US Geological Survey (USGS) quadrangles 

 were selected as base maps for this project (Figure 18). They were revised by 

 the Cartographic Revision Section of the Photogrammetry Division of NOS with 

 l:24,000-scale color photography taken in 1982-83 at near high water, covering 

 all of the ocean coast within the project area. Historical shoreline data, 

 obtained from NOS and USC&GS topographic surveys (T sheets) compiled since the 

 early 1800's, were added to the base maps. Table 2 lists dates of historical 

 T sheet surveys available for each base map. 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. 



47. Copies of all historical maps used as source data in this study 

 were obtained from the NOS vault in Riverdale, MD, through the NOS Reproduc- 

 tion Division. Copies were initially bromide prints (a photographic process 

 that provides a long shelf- life copy) and were later made into more stable 

 matte- finish film positives. 



48. Topographic surveys are the basis for delineation of shorelines on 

 nautical charts published by NOS. Present and historical surveys map the mean 

 high-water line (MHWL) as the shoreline. According to Shalowitz (1964), the 

 authority on historical significance of early topographic surveys of NOS, "The 

 most important feature on a topographic survey is the high-water line." Accu- 

 racy of the early surveys was addressed before any of the historical dates 

 were used in this study. 



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

 Survey, issued the earliest instructions for topographic work. Those 



38 



