reduced to position (X,Y) and depth (Z) triplets relative to the local NGVD. 

 The data were listed, and a display of the profiles (i.e., distance along the 

 range versus elevation) using line printer graphics was generated for visual 

 inspection. After the data had been edited and determined to be acceptable, 

 another set of routines was used to compute various statistics (i.e., maximum 

 and minimum sand elevations) and displays (i.e., graphic profile representa- 

 tions, envelopes of elevations, and time sequences of elevations), as in 

 Appendix C. 



78. The offshore portion of the October bathymetric survey showed an 

 "artificial" rhythmical bending of the bottom contours. Errors in the off- 

 shore portion are believed to have been the result of (a) using a floating 

 surveying platform, (b) not performing a bar check calibration of the fathom- 

 eter (i.e., calibrating at various depths and positions along the range), and 

 (c) not accounting for wave motion in the fathometer data. At greater depths, 

 stratification of the water temperature, water density, and thermoclines would 

 have affected the accuracy of the measurements. Because of the low slope in 

 the offshore region, small errors in elevation resulted in significant excurs- 

 ions of the contours. Although the fathometer depth data seaward of the pier 

 end are believed accurate to ±0.2 m, caution should be exercised when the data 

 are used. 



Photography 



Aerial 



79. Quarterly aerial photographic missions were performed by a contrac- 

 tor as part of the measurement program using a 9-in. negative format mapping 

 aerial camera capable of black and white and color photography. All coverage 

 was at least 55 percent overlap, with all flights flown as close as possible 

 to periods of low tide and between 1000 and 1400 hours with less than 10 per- 

 cent cloud cover. 



80. The flight lines were concentrated near the FRF although one flight 

 line extended from Cape Henry, Virginia, to Cape Hatteras, North Carolina. 



The flight lines and scale specifications are shown in Figure 6. 

 Beach 



81. As part of the visual observations, daily color slides of the beach 

 were taken using a 35-mm camera from the pier looking north and south. The 



' 32 



