The primary horizontal control network furnished the basic controls Reproduced from the holdings of the National Archives Pacific Southwest Region from which the relations of test structures were determined. The scheme was expanded to inolude the photo stations at sites M, N, P and Q; C, E and V Zero points, and the islands of Bogon and Rigili. The islands of Murin and Aeraanbiru were looated from controls established in the local Zero areas, General Features The specifioations and criteria for second order triangulation were followed in expanding the scheme. While the strength of figure was weak in some cases, additional observations were taken which offset the weakness. All observations were made at night, and standard procedure was attempted throughout. Weather conditions and interference from construction and scien- tific work in the tower areas affected the survey, but the results are considered consistent with requirements. A quadrilateral was developed including station Bokon, thereby increasing the strength of this station over the single triangle by which it was previously located. The adjusted values vary slightly from those recorded from the previous survey. Station Islet was also strengthened by inclusion in a quadrilateral with no change in the values previously recorded. The location of station Rigili is to third order acouracy, which conforms with instructions regarding location of this station. Field Computations Computations of the expanded soheme were made at the jobsite. While adjustments to balance out observing errors were not made, the results were within solentific requirements. (32