CHAPTER Ii, SECTION 1A increased the efficiency in observing as the in- 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 mitted to the observing personnel. This was often order traverse specifications on site Fox, 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 campsat site Tare and site Charlie and were quartered on an LSU for observing in the eastern portion of the lagoon. Considerable time was iost 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 Due to the velocity of wind in the ares, 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 parallei to the line on the windward side as each measurement was made. GEOGRAPHIC POSITION. The origin of geo- graphic position of the USN Survey, completed in 1946, is based on scaled values from a Japanese chart. As the accuracy of this chart was con- sidered satisfactory for publication of a hydro- graphic 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 considered to justify the additional expense to the survey. USN Station Air on site Oboe is common to both the \'SS Sumner and USS Bowditch surveys. As this station was recovered and was in a desirable location for this purpose, it was adopted evening as practical. The intensity of the target lights was adjusted to the minimum which couid be observed, thereby obtaining the most refined pointing. One or more sets of eight positions each were observed. When the results obtained are latitude 1. 30-24.906 North, longitude 16524-55.168 East. Geodetic Survey no attempt was made to obtain further refinement. GEODETIC AZIMUTH. Examination of the USN Survey re ords shows that three static~sAir, South, and “inyu are common to bot. the were within specifications of the U.S. Coast and 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 isiand, it was necessary to establish a broken base consisting of two sections, Oboe-Piper and Piper-Salt. 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 theodcolite and the measurement was made with three Lovar tapes using thermometers and stretcher apparatus of 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 as the orig.n of geographic position for this survey. The USN edjusted values for the station USS Sumner an: USS Bowditch network- che two surveys were combined in an adjuscment which adopted « stellar azimuth observed by the USS Sumner as the origin of geodetic azimuth. It was intended to include a triangie formed by these three stations in the network of the new survey and accept a mean value obtained from the directions Air-South and AirEnyu as the origin of azimuth. However, as 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. hoe PLANE COORDINATES-CASTLE GRID. A plane grid has been established common to the ot ' "e 4 i Page 2-23 ho 1 | 1 we pL } ? ' — ne necessary due to weather conditions and permitted communication when light signals would have failed. for local trianguiation was established to first me tensity of the target lights could be adjusted instantly and changes in plans could be trans- AOD PE a il ee re Portable radios were used for this purpose and