The nearshore bottom elevations along the north side of the FRF pier var- 

 ied as much as 3.3 meters at pier station 6+51, located 130 meters seaward of 

 the dune, and as little as 0.5 meter at pier station 12+47, some 312 meters 

 from the dune . 



III. INSTRUMENTATION 



This section identifies the instruments used for the long-term monitoring 

 of oceanographic and meteorological conditions, and briefly describes their 

 design and operation. More detailed explanations may be found in Miller 

 (1980). The equipment used for collecting other types of data (e.g., survey- 

 ing system) is discussed in Section IV. 



1. Wave Gages . 



Five wave gages are in operation as part of the BEM for monitoring the 

 wave conditions in the vicinity of the FRF (Fig. 2). These include a wave 

 staff gage on Jennette's Fishing Pier in Nags Head, North Carolina, approxi- 

 mately 40 kilometers south of the FRF; two wave staff gages on the FRF pier 

 (one at station 6+20, the other at station 19+00); and two Waverider buoy 

 gages located 0.6 and 3 kilometers offshore. 



The wave staff gages are parallel cable types manufactured by the Baylor 

 Company, Houston, Texas. These gages are designed for an accuracy and reso- 

 lution of 1 and 0.1 percent full scale, respectively. The Waverider buoys 

 are manufactured by the Datawell Laboratory for Instrumentation, Haarlem, 

 Netherlands. The 0.7-meter-diameter buoy floats on the water's surface and 

 measures the vertical acceleration produced by the passage of a wave; the buoy 

 electronics doubly integrate this signal to produce a displacement signal and 

 telemeter the signal to a receiver onshore. The manufacturer states that wave 

 amplitudes are correct within 3 percent of their true value for frequencies 

 between 0.065 and 0.5 hertz (i.e., wave periods between 15 and 2 seconds). 

 For frequencies as low as 0.03 hertz (i.e., a 33-second period), the manu- 

 facturer provides a frequency response curve which must be used to maintain 

 the 3-percent accuracy. The frequency response curve was not used for the 

 data in this report; wave periods greater than 15 seconds were noted in less 

 than 2 percent of the Waverider observations. 



2 . Tide Gages . 



Water level data from two gages located on the FRF pier are presented in 

 this report. The National Oceanic and Atmospheric Administration (NOAA), 

 National Ocean Survey (NOS) , control station at the seaward end of the 

 research pier (station 19+60) consisted of a Leupold-Stevens gage manufactured 

 by l£upold and Stevens, Inc., Beaverton, Oregon. The nearshore station along 

 the pier (station 7+20) consisted of a Fischer-Porter gage manufactured by 

 Fischer and Porter Company, Warminster, Pennsylvania. Both the leupold- 

 Stevens and Fischer-Porter analog-to-digital recorders are float-activated, 

 spring-counterbalanced instruments that mechanically convert the vertical 

 motion of a float into a coded, punched paper-tape record. The below-deck 

 installation at stations 19+60 and 7+20 consisted of 30.5-centimeter-diameter 

 stilling wells with a 2.5- and a 1.3-centimeter orifice, respectively, and 

 21.6-centimeter-diameter floats. 



12 



