Figure 2-2. Geodimeter and portable data acquisition computer 



major test, the profile was surveyed along the center line of the channel and 

 on lines located 3 ft from each of the channel walls to assess uniformity of the 

 profile across the channel. The three survey lines were designated as Line 3, 

 Line 6, and Line 9 to denote locations as 3, 6, and 9 ft (0.9, 1.8, and 2.7 m) 

 from the channel west wall; because the channel is 12 ft (3.66 m) wide, 

 survey Line 6 is the center line. Three-line surveys were also occasionally 

 made if cross-tank flow was observed or suspected. Between wave runs of a 

 given test, surveys were made only along the center line to allow wave action 

 to resume as soon as possible (Figure 2-4). 



The beach profile survey procedure was designed to optimize speed, 

 accuracy at a given survey point, and resolution of profile features. The coor- 

 dinate system origin was chosen to coincide with the first of a series of instru- 

 ment mounts (channel stations described in Chapter 1) located along the wall 

 of the channel, and the top of the channel west wall was chosen as zero in the 

 vertical. The horizontal coordinates were defined such that the x-axis was 

 positive directed offshore, the cross-channel coordinate y was positive directed 

 across the channel, and the vertical (z) axis was positive directed upward, to 

 form a right-handed coordinate system. 



It was difficult to zero the station on the origin due to glare from the win- 

 dows of the enclosure and closeness of the origin to the Geodimeter. There- 

 fore, a backsight was chosen at a known distance further along the channel. 

 The coordinates from the origin to the Geodimeter and from the origin to the 

 backsight were specified to the data-acquisition program for computing a 



Chapter 2 Beach Profile Surveys and Sediment Sampling 



43 



