Before the outbreak of hostilities there were certain areas whose tidal 

 characteristics could as a whole be considered as having been adequately 

 determined. Representative of such areas is the Pacific Coast of the 

 United States, where the U.S. Coast and Geodetic Survey has maintained 

 primary tide stations in continuous operation for many years. Along 

 this particular coast tide data are also available for hundreds of inter- 

 mediate tide stations, occupied primarily as vertical control stations for 

 hydrographic surveys. 



To a somewhat lesser degree there may also be included in the regions 

 of generally adequate tidal coverage the Pacific Coast of Alaska, the 

 Hawaiian Islands, and the Philippine Islands. Particularly is this true 

 of south-eastern Alaska. More detailed development of the complicated 

 tidal movements in the Aleutian Islands and Bering Sea areas can be ex- 

 pected from primary tide stations established during the war and from 

 hydrographic operations now actively in progress in these areas. Fortu- 

 nately, most of the tide records which had accumulated from many years 

 of survey operations in the Philippine Islands had been transferred to 

 the United States before the beginning of hostilities and were immediately 

 available in the files of the U.S. Coast and Geodetic Survey for the detailed 

 analyses to be demanded by war operations. 



Until recent years there were long sections of the Pacific Coast of Cen- 

 tral and South America for which little observational tide data were 

 available. An opportunity to improve this situation was presented 

 when in 1940 arrangements were completed for a programme of tidal 

 investigations in co-operation with American republics. 



In carrying out this project the U.S. Coast and Geodetic Survey, in 

 co-operation with the countries involved, established twelve tide stations 

 at, selected localities in the area between Central Mexico and Southern 

 Chile. By 1942, w^hen the installations were completed, there existed a 

 simultaneously operated chain of primary tide stations covering the 

 entire Pacific Coast of the x\mericas from the Aleutian Islands to Magellan 

 Strait. 



The records obtained as the result of this programme have been sub- 

 jected to detailed analysis, with the result that along this coast, where 

 tidal information was formerly meagre, there are now key locations where 

 the harmonic constants and other tidal characteristics are reliably estab- 

 lished. These stations can now serve as control points to which second- 

 ary stations may be referred by comparison of simultaneous observations. 

 They also provide more precise data on the types of tide which character- 

 ize this area ; information that is necessary for planning to best advant- 

 age the location of needed additional stations. It is expected that 

 present and proposed mapping operations by the Inter-American Geo- 

 detic Survey and the individual countries will result in a much closer 

 spacing of tide stations for local control purposes with a corresponding 

 increase in tidal knowledge for intermediate coastal areas. 



During the war period the U.S. Coast and Geodetic Survey was 

 called upon to assemble tidal information for Pacific Ocean combat areas. 

 This information was prepared in the form of special reports dealing 

 with specific areas and covered the entire Pacific coast-line from Bering 

 Sea to the Dutch Indies, including the island groups w^est of the Date 

 Line. Since coverage of the areas involved was required to be as complete 

 as possible, every available source of relevant material was consulted and 

 utilized in the processing of these investigations. Not only did these 



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