Total survey station 



A Geodimeter T140 total survey station was positioned outside of the tank 

 (Figure 2-2) to track by an infrared beam the position of the prism mounted 

 on the top of the rod. The Geodimeter obtained power from a 12-V battery. 

 The coordinate system reference angle was set to zero on a back sight located 

 on the wall of the channel. The maximum horizontal distance from the station 

 to the channel was limited by the presence of the north wall of the envi- 

 ronmental enclosure of the O. H. Hinsdale Wave Research Laboratory 

 (WRL), Oregon State University (OSU), where SUPERTANK was conducted. 

 Accuracy of the coordinates of the station is discussed below. Additionally, 

 the Geodimeter was used to measure instrument locations, including current 

 meters and sediment sensing instruments mounted in the channel, and video 

 cameras located far from the channel. 



Survey data acquisition program 



The output signal from the Geodimeter was directed to a portable PC 

 located on a raised table next to it (Figure 2-2). The PC ran a program writ- 

 ten by Mr. William Birkemeier, Chief of the FRF, specifically for use with a 

 total survey station. With the Geodimeter position, backsight information for 

 a known point in the coordinate system, and prism elevation given, the pro- 

 gram computed the horizontal and vertical coordinates of the bottom profile or 

 other survey targets, such as repositioned gauges when the channel was 

 drained. 



The interactive data collection program displayed measured coordinates as 

 they were read by the Geodimeter. The readings and input conditions used in 

 the calculations were also written to a file by the program. The menu-driven 

 program provided several features, including the capability to pause recording 

 of data when the survey was interrupted (e.g., for routine lowering of the 

 movable guide on the survey carriage). Other features included the capability 

 to mark certain data points in the file corresponding to features of interest 

 along the profile, such as location of the still-water line, the maximum point 

 of runup, or a location where severe scarping had occurred. 



42 



Experiment Procedures 



Profile survey 



Procedure. Typically, 15 min were required to ready all equipment and 

 survey the profile with a nominal horizontal spacing of 1 ft (0.3 m), but with 

 much finer resolution over features such as dunes, steps, and bars, which had 

 large across-shore gradients in elevation. Figure 2-3 shows a plan view sche- 

 matic of the arrangement of the survey equipment. At the start and end of a 



Chapter 2 Beach Profile Surveys and Sediment Sampling 



