to meet project requirements, a substantially new and stronger scheme Pacific Southwest Region Reproduced from the-holdings of the National Archives was necessary which could be expanded as required. 1949-50 HORIZONTAL CONTROL SURVEY This survey was designed to meet the requirements of Operation Greenhouse and adaptable to future expansion. It consisted of sixteen stations covering the Eastern portion of the Atoll from Bogallua island to Eniwetok island and included five atations of the previous surveys. As it was determined that Station North Base had been disturbed it was necessary to measure Base #2-Runit to second order accuracy. a new base line North The network expanding from this base line was executed to second order specifications and procedure of the U. S. Coast and Geodetic Survey. The geographical position of Station Runit and the agimuth of the line Runit-Coral, as determined by the previous survey, were adopted as the origin of position and agimuth. 1951 EXPANSION An expansion of the survey was necessary to meet additional requirements which could not be anticipated earlier. Several additional islands were located by local triangulation and photo tower and zero locations were determined. on all project islands. Local control traverses were established The accuracy of these controls depended on their uses and were generally of third order. The zero lines and some traverses for location of instrumentation were established to first order traverse specifications. An independent plane coordinate grid was established at each of the zero areas for location of instrumentation. While satisfactory re- Sults were obtained it brought out the desirability for an overall Atoll grid.