CHAPTER It, SECTIONS 1-1A field inspectors to the greatest extent possible. The weekly progress report detailed activity on open construction work orders which reached 4 maximum number of 337 on the Eniwetok Atoll and 339 on the Bikini Atoll for a total of 676. SECTION IA SURVEYS Surveys by Holmes & Narver at the Pacific Proving Giound were initiated at Eniwetok Atoll in February 1949 with the topographic mapping of project islands for design ‘surposes. As additioral personnel arrived, the activities of the department expanded to include a hor- izontal control network, additional torpograpny, hydrograph, construction lafout, and special surveys to satisfy scientific requirements and to provide assistance to Users. Surveys at Eniwetok were a continuation and expansion of these activ:ties to fit the special needs of three test operations. With the expansion of the PPG to include Bikini Atoll, a survey progrem was initiated in this area following the same general pattern of surveys previously performed in the Eniwetok Atoll area. The majority of the survey personnel were stationed at Bikini Atoll duting the CASTLIE program with a maximumof six field parties and supporting office personnel. The smaller program at Eniwetok Atoll was served by two field parties with some transfer of personnel between areas to meet peak work loads. The sequence of surveys at both areas was dependant’ on priorities for the services of the. department. As construction layout proceeded simultanecusly with design and contra) surveys, it was not possible to follow the normal pro- cedure cf first establishing horizontal and vertical control and then proce -ding in sequence through design surveys and ccnstruction layout. This condition did not permit maximum efficiency in performing the design and control surveys, but as construction layout was kept on a current basis at all times, the procedures used were just- ified. The earlier surveys were covered in detzil in reports of OPERATIONS GREENHOUSE and IVY, and the following is primarily a description of survey activities at Bikini Atoll thr- ough the CASTLE program. In view of the recoverabilitvy of the work and its probable future value in any use of the area, however, sufficient historical summaryis given to evaluate its cartogrephic significance. HORIZONTAL CONTROL — ENIWETOK ATOLL A horizontal control scheme was es:ablished in 1949-50 covering the eastern portion of the Atoll. This scheme was expanded in 1951 and 1952 to include the entire Atoll and consisted of primary network of second order triangul- ation stations supplemented with third order stations at locations of lesser importance. Test operations destroyed some of the original stations and new stations were established, as required, by expansion from the remaining por- tions of the network. Records of these surveys are included in the completion reports for OP- ERATIONS GREENHOUSEand IVY. PREVIOUS SURVEYS. A study of previous survevs within the Atoll was made and some features of these surveys were utilized in establishing the scheme. The available records of these surveys are included in “The Report of the Engi- neer, Joint Task Force SEVEN, Part 2,” dated 1948. The earliest survey was completed in 1944 by the USS Bowditch to control the hydrographic mapping of the Atoll. This survey was of third order accuracy. and as mostof thestations were not on project islands it was not ad- aptable to requirements of this project. However, the Bowditch geographic position of Stat- ion North Base on Runit Island and the azi- muth of the line Station North Base-Stacien Sand becamethe origin of positior. and azimuth tor the later surveys. A survey was completed in 1947-48 by Joint Task Force SEWEN, consisting of a limited scheme covering the eastern portion of the Atoll. The scheme was reported to be of first order accuracy but it was only because of its limited extent that it could be considered to Le of such high order. As the south ena of the original (USS Bowditch) base line had been destroyed, a new base line, North Base-Runit, was established and the azimuth of this line was computed from its relation to the line North Base-Sand. Expansion of this scheme involved re-occupation of all of its existing stations and it became obvious that to meet project uirements, a substantially new and stronger scheme was necessary which could be expanded as rquired. 1949-50 HORIZONTAL CONTROL SURVEY. This scheme was designed to meet the control requirements of. OPERATION GREENHOUSEand to be adaptable to future expan- Page 2-6 ad