1952 EXPANSION AND ADJUSTMENT Reproduced from the-holdings of the National Archives Pacific Southwest Region Requirements for Operation Ivy resulted in the expansion of the scheme to include the entire Atoll. Some stations of the earlier surveys had been destroyed and additional stations were required. Fifteen stations were established, replaced or more precise values determined. AS the expansion permitted dosing the survey around the Atoll to the Runit base line a check on tne previous work was obtained. The closing error of the survey before adjustment was determined a8 approximately 1:25000. An additional cheok was obtained by inclusion of the zero line traverse in the Flora-Gene area. This indicated a closing error of approximately 1:70000 before ad justment of the adjacent quadrangle. In order that the values of a station would remain the same independent of the direction of computation through the net an adjustment has been applied to the triangulation figures. This consists of a side equation adjustment which resulted in slight changes in the values previously reported but of little consequence in computations made to date. | PLANE COORDINATE SYSTEM (IVY GRID) A plane coordinate system has been established which is common to all stations. MThe origin of coordinates is a plane through tri- angulation Station Coral with assumed values of N 100,000. 100,000, at this station. used as East A true meridian through this station was the basis of bearings and was determined by computing through the base expansion figure from the adopted azimuth of the Runit base line. Tne horizontal control network -3- as it now exists should meet