(c) For offshore surveying, the contractor used a large fishing 

 (sport) boat with an analog fathometer; two people on shore trian- 

 gulated the boat's position. The fathometer was calibrated on each 

 range line by comparing the value at the sea sled's seawardmost posi- 

 tion. The range, angle, and depth Information was correlated and 

 manually reduced to produce position and depth data. 



In addition to the beach and bathymetrlc surveys, weekly profiles along 

 both sides of the pier were performed, using the "lead-line" surveying tech- 

 nique which consisted of lowering a weighted measuring tape and noting the 

 distance below the pier deck which Is a known elevation above NGVD. Spaces 

 between the pier bents (I.e., every 12.2 meters) were used to minimize inac- 

 curacies due to scour near the pilings. 



b. Data Analysis . Surveying conditions were calm in 1979 and no correc- 

 tion for wave effects was made by the contractor for the offshore part of the 

 bathymetrlc survey. An output of the data for the pier, beach, nearshore, 

 and offshore sections of each range is generated and a graph of the profiles 

 (i.e., distance along the range versus elevation) is provided, using line 

 printer graphics, for visual inspection. After the data are edited and deter- 

 mined to be acceptable, another set of computer routines is used to generate 

 various statistics, e.g., maximum and minimum sand elevations, and various 

 graphic displays, e.g., profile representation, contour movement, envelope of 

 elevations, and time sequence of elevations. 



6. Photography . 



a. Aerial . Several aerial photography missions were performed by a 

 contractor as part of the BEM, using a 9-inch negative format mapping aerial 

 camera for both black and white and color photography. All coverage had at 

 least a 55-percent overlap, and all flights were flown as close as possible to 

 periods of low tide between 1000 and 1400 hours with less than a 10-percent 

 cloud cover. The flight lines were concentrated near the FRF although one 

 flight line per year extended from Cape Henry, Virginia, to Cape Hatteras, 

 North Carolina (see Fig. 5). The flight dates and scale specifications are 

 described in Table 2. 



b. Ground. As part of the visual observations, color slides of the beach 

 were taken daily from the pier looking north and south, starting in August 

 1979. The location from which the picture was taken, the date, the time, and 

 a brief description of the picture are marked on the slides, and an inventory 

 is maintained. 



V. RESULTS 



Although this report is Intended to provide basic data for analysis, many 

 of the dally observations have been summarized by month, season, or year to 

 aid in Interpretation. Where summaries appear and no individual data are 

 Included in the report, users may obtain the detailed information by following 

 the procedures described in Section VI. 



22 



