In the next step, a base map was produced onto which T sheet or photo data 

 could be transferred. The state plane coordinate system intersections on the 

 T sheets served as a set of primary control points. Manmade and natural 

 points acted as secondary controls. The relative position of each control 

 point was determined with an X-Y digitizer. Since state plane coordinates 

 were known for the primary control points, a program (CONVERT), developed by 

 NOS, was used to transform all digitized secondary control points into state 

 plane format. These points were then plotted onto mylar at a 1:10,000 scale 

 by means of a second computer program (P2NDPT) and a Calcomp plotter. The 

 mylar sheet became the base map onto which shoreline data were transferred. 



Concurrent with the production of the base maps, aerial photos were 

 annotated to highlight ocean and bay shorelines, dunes, shrubs, marshes, and 

 washovers. Distinctions were not made among dunes, shrubs, and washovers on 

 the early U.S. Coast Survey charts, and these units were combined into one 

 category. All data were transferred onto base maps with a Bausch and lomb 

 zoom transfer scope (ZTS). 



Individual photos were optically overlaid on the base maps. Scale and 

 stretch adjustments were made until the optimal fit between the control points 

 on the photo and base map was achieved. Perfect alinement of all control 

 points was not possible, because the ZTS does not correct for tilt. Once the 

 best possible fit was achieved, however, most of the distortion was removed. 

 After the base maps were completed, coordinates were determined using the X-Y 

 digitizer for shorelines and vegetation community boundaries. It was possible 

 to produce any desired map or set of overlay maps with different scales, 

 levels of detail, or line type with the plotting programs. 



The length of each major unit of the Nauset Spit system was calculated 

 from each historical map. Shoreline changes were measured at bl-meter (200- 

 foot) intervals along the entire spit system. The average, minimum, and max- 

 imum barrier widths were calculated at 305-tneter (1,000 -foot) intervals. 

 Areas for dune, salt marsh, and shrub communities, and for washovers and 

 supratidal sandy environments, were determined with a polar planimeter on a 

 large-scale map (1:2,400). The location of loss or gain of total barrier area 

 was determined for sequential pairs of overlaid maps (1:12,000) using a dot 

 grid (256 dots per square inch). Distinctions were made for areas gained and 

 lost along the ocean, bay, and at the spit terminus. Sequential map overlays 

 (1:12,000) were used to delineate the location of dunes and salt marshes that 

 wera lost and those that developed between the mapping periods; these changes 

 were quantified with a dot grid. 



c. Nauset Splt-Eastha m. The southern 2.1 kilometers of Nauset Spit- 

 Eastham has changed dramatically in the last 122 years due to the migratory 

 characteristics of Nauset Inlet (Fig. 102; Table 41). Only a single spit 

 extended southward from the Eastham headlands near the Nauset Coast Guard 

 Station in 1856. The destruction of the drumlin described by Champlain in 

 1605 (Fig. 95) led to the landward migration and dissolution of the south 

 spit. Salt marshes to the lee of this spit were buried by shifting sands 

 during the 1830's (Nickerson, 1931). The north spit extended southward to a 

 position west of the former south spit. By 1856 Nauset Inlet was located at 

 the base of Nauset Heights and the north spit was 4.9 kilometers' long. 



166 



