PART II: PROFILE DATA 



8. This part describes the methods used to survey the profile data and 

 identifies potential sources of error and how errors were handled. The data 

 for each profile line are a series of distance-elevation pairs measured during 

 a repetitive number of surveys. The data extend from a shore-parallel base- 

 line, located landward of the duneline, out to a usual depth of 8 to 9 m. 

 Elevation data are referenced to the 1929 National Geodetic Vertical Datum 

 (NGVD) using third-order control established at the FRF. Each survey of each 

 profile line is uniquely identified by a profile number and survey number. 



9. Surveys were initially conducted biweekly, the northern lines one 

 week followed by the southern lines the next. This sequence changed in Decem- 

 ber 1982 to biweekly surveys of all four lines. Full bathymetric surveys of 

 15 to 28 lines surrounding the FRF were also conducted monthly. Additional 

 surveys were added to cover significant storms and in support of special 

 experiments. The time interval between surveys varied from 1 to 44 days. 



The CRAB 



10. The method used to collect the majority of the profile data is des- 

 cribed in Birkemeier and Mason (1984). All profiles were surveyed using the 

 FRF Coastal Research Amphibious Buggy (CRAB) shown in Figure 4. Built by the 

 Wilmington District of the US Army Corps of Engineers, this unique three- 

 wheeled vehicle was modeled after a vehicle originally built by Marine 

 Travelift & Engineering of Sturgeon Bay to monitor a Corps of Engineers beach 

 nourishment project. 



11. The CRAB consists of a tripod of 20.3-cm schedule-80 aluminum 

 tubing, connected at the base by horizontal members 2.1 m above the ground, 

 and an operations platform 10.7 m above the ground. Power is supplied by a 

 39.5-kW Volkswagen engine on the deck which drives a variable stroke hydraulic 

 pump. This pump transfers hydraulic fluid at 5.5 x 10° N/m^ or higher to 

 hydraulic motors at each of the wheels. The variable stroke feature of the 

 pump allows an infinitely variable gear ratio in either forward or reverse and 

 constant engine speed. For strength and corrosion resistance, all hydraulic 

 lines are stainless steel except for short flexible sections at the front 

 steering wheel. 



