CHAPTER II, SECTION 1A Portable radios were used for this purpose and increased the efficiency in observing as the intensity of the target lights could be adjusted instantly and changes in plans could be trans- mitted to the observing personnel. This was often necessary due to weather conditions and permitted communication when light signals would have failed. The observing program started in May 1953. The observing party consisted of an observer, recorder and a varying numberof light tenders. The personnel operated from camps at site Tare and site Charlie and were quartered on an LSU for observing in the eastern portion of the lagoon. Considerable time was lost due to rain and high wind velocity and the program was delayed by the priority of other surveys. Transportation was adequate but water transportation by LCM, DUKW and LCU was necessarily slow. Helicopters were not available until late in the observing program. It was generally necessary to distribute the personnel late in the afternoon and return them to their base of operations the following morning. The value of the helicopter was demonstrated during the latter part of the survey. The observing was started as early in the evening as practical. The intensity of the target lights was adjusted to the minimum which could be observed, thereby obtaining the most refined pointing. One or more sets of eight positions each were observed. When the results obtained were within specifications of the U. S. Coast and Geodetic Survey no attempt was made to obtain further refinement. the U.S. Coast and Geodetic Survey and with Lovar tapes and chaining bucks similar to the Oboe-Salt base line measurement. A base line for local triangulation was established to first order traverse specifications on site Fox. Due to the velocity of wind in the area, it was generally necessary to provide a windbreak in order to obtain accurate results. The windbreak used consisted of a 36-inch strip of canvas approximately 55 meters in length, which was held parallel to the line on the windward side as each measurement was made. GEOGRAPHIC POSITION.The origin of geographic position of the USN Survey, completed in 1946, is based on scaled values from a Japanese chart. As the accuracy of this chart was considered satisfactory for publication of a hydrographic chart of the Atoll and for origin of position for the USN Survey, the refinement which could be obtained by astronomic observations for geographic position was not con- sidered to justify the additional expense to the survey. USN Station Air on site Oboe is common to both the USS Sumner and USS Bowditch surveys. As this station was recovered and was in a desirable location for this purpose, it was adopted as the origin of geographic position for this survey. The USN adjusted values for the station are latitude 11-30-24.906 North, longitude 16524-55.168 East. GEODETIC AZIMUTH. Examination of the USN Survey records shows that three stationsAir, South, and Enyu are common to both the OBOE-SALT BASE LINE. The base line for the network extended from Station Oboe on Oboe to Station Salt on Sugar. Due to the configuration of the island, it was necessary to establish a broken base consisting of two sections, Oboe-Piper and Piper-Salt. USS Sumner and USS Bowditch networks. The two surveys were combined in an adjustment which adopted a stellar azimuth observed by the USS Sumner as the origin of geodetic azimuth. It was intended to include a triangle formed by these three stations in the network Standard procedure of the U. S. Coast and Geodetic Survey for second order base line measurement was followed. Angles were measured with the Wild T-2 theodolite and the measurement was made with three Lovar tapes using thermometers and stretcher apparatus of tained from the directions Air-South and AirEnyu as the origin of azimuth. However, as an approved type. Stakes were set at 50 meter intervals for chaining bucks, and the tapes were alternated so that in completing the forward and backward measurements all three tapes were used in each direction. The computed probable error of total measurement is one part in 2,800,000. FIRST ORDER TRAVERSE. The relations between Stations 50 and 2210 at site Tare and 20 and 1201 at site Charlie were required to a tolerance of not to exceed 1:25,000. This requirement was accomplished by first order traverse measurement following standard procedure of of the new survey and accept a mean value ob- Station South was not recovered, the USN value for the forward azimuth of the line Air-Enyu was adopted as the basis of geodetic azimuth. A check triangle including Station Kans of the USN Survey resulted in a computed difference of directions at Station Air of 0.4”. This was considered to be within project requirements for orientation of the scheme. The USN adjusted value for the forward azimuth of the line AirEnyu is 268-00-01.4 or N88-00-01.4E. SCIENTIFIC AZIMUTH. Geodetic azimuths are computed in a clockwise direction from south. The azimuths used in the description of Scientific Stations are computed in a clockwise direction from north. PLANE COORDINATES-CASTLE GRID. A plane grid has been established common to the Page 2-23