transport difficult . A flush cargo deck and hydraulically actuated ramp 

 provide convenient access for personnel and wheeled-equipment. The 

 LARC-XV is capable of negotiating breakers 10 feet high either onto 

 or off the beach. With a fuel capacity of 360 gallons, it has a marine 

 consumption rate of approximately 30 gallons per hour. 



The LARC-V has become a standard amphibious vehicle, and its avail- 

 ability for radioisotopic tracing operations is fairly well assured. The 

 LARC-XV, however, has had limited production and distribution, and might 

 not be available for project-oriented searches when and where it is 

 needed. It is judged that at the end of the present program, instru- 

 mentation will be refined to a highly transportable package that will 

 permit operations aboard the smaller LARC-V or similar vessel. Actually, 

 where environmental conditions are not severe and a hoisting device is 

 not necessary, the present on-board instrument shelter will function on 

 a LARC-V. 



The Marine Corps Landing- Force Development Center at Camp Pendleton, 

 California, furnished a driver to instruct the crew in operation and 

 maintenance of the amphibious vehicles. 



The search operation requires a constant knowledge of the searcher's 

 position. To save time and money, an accurate, fast position-finder is 

 needed to determine the position of the radiation detector as it is towed 

 behind the survey vessel. Transit and alidade techniques are slow, re- 

 quiring two or more operators, and are not easily used with computers. 

 The various radar navigational devices normally used by ships are not 

 accurate enough to locate the surface craft within a few feet. Without 

 precision, the search director could unknowingly miss hundreds of square 

 feet of test area. 



Without high-resolution positioning data, the configuration of dis- 

 persal patterns could not be accurately defined. 



The Cubic Autotape System was evaluated as the most suitable navi- 

 gational system available for the RIST study. The Autotape is a compact 

 transistorized system which employs microwaves along the radio line of 

 sight to establish ranges (distances) to the surface craft from shore- 

 based responders. The system simultaneously measures the distance be- 

 tween each of the two responders and the boat-borne interrogator through 

 a phase comparison of modulated frequencies. With a range of 30 miles, 

 it has a resolution of 1 meter. The responders are battery-operated 

 and can be left unattended while in operation. 



For the RIST study, normal land surveying procedures are used to 

 establish responder sites on major and minor coastal promontories. 

 Distances between adjacent responders vary from 1,000 to 3,000 feet 

 depending upon accessibility and their alinement with the search area. 



Aboard the surface craft, the 2-range interrogator visually displays 

 the distances to the responders in meters (Figure 12). The position of 



20 



