Section A. INTRODUCTION 



In 1966 the Coastal Engineering Research Center (CERC), in coopera- 

 tion with the Atomic Energy Commission, initiated a 3-year radioisotopic 

 sand tracer study of littoral transport around Point Conception, Cali- 

 fornia. The purpose was to develop and use radioactive tracers for 

 research in sand movement and littoral processes. The objectives 

 included determination of suitable radioactive isotopes, development of 

 handling and survey procedures, and development of computer programs for 

 editing, processing and graphical display of the data. At the same time, 

 studies of sediment transport around the Point Conception headland and 

 of the mechanics of littoral transport were conducted. Methods developed 

 by this program have direct application to engineering design of harbor 

 development and beach erosion prevention, and quasi-military application 

 such as the location of radioactive and other toxic materials. 



Sand grains indigenous to the study area are labeled with a radio- 

 isotope that does not adversely affect their hydraulic properties. A 

 mobile detector system, using cesium iodide crystals and housed in a 

 "ball" towed behind an amphibious vehicle, detects the location and 

 intensity of the radiation. Concurrently, additional field data are 

 collected on sediment size and composition, isotope distribution, beach 

 and nearshore bottom topography, weather, and sea and swell conditions. 



During a sand-tracer field investigation, radiation measurements are 

 made continuously as the mobile detector system is towed along a beach, 

 through the surf, and over the offshore bottom. With a time selection 

 mode for data acquisition available in increments from 0.1 to 10.0 

 seconds, a large mass of data is accumulated in a few hours. During a 

 field test, surveying may go on several hours a day for several weeks. 

 Computer processing is necessary to study and evaluate the great volume 

 of collected data. Plotting and posting of the survey data is also use- 

 ful for monitoring field operation. 



The initial field investigations at Surf, California, relied on 

 manual preparation of maps and subjective interpretation of data printed 

 by the teletype of the onboard data acquisition system. It immediately 

 became evident that computer processing and plotting must be employed in 

 future operations, and 'CERC undertook development of computer programs 

 to generate plots useful to continuing field operations. This specific 

 program is called RAPLOT. The first version of the program was used to 

 process the data collected in the December 1967 field test at Point 

 Conception, California, and is documented in Appendix D of CERC report, 

 M.P. 2-69, by Duane and Judge (1969). RAPLOT was originally compiled 

 and made operational on the UNIVAC 1108 at the National Bureau of Stand- 

 ards, with graphic display on a Benson-Lehner incremental plotter at CERC. 

 Later, the program was adapted to the IBM 7094 Computer and Milgo plotter 

 at the Western Test Range of Vandenberg Air Force Base. This version of 

 the program was used to support later field tests at Point Conception 

 and Surf, California, in September and October 1968 and in February and 

 June 1969. 



