1. GENERAL REQUIREMENTS 



1-1 Introduction. — To provide charts and 

 related information for marine and air com- 

 merce, and to provide basic data for en- 

 gineering and scientific purposes, and for 

 other commercial and industrial needs, the 

 Coast and Geodetic Survey is authorized by 

 law to conduct a variety of field and office 

 activities. These include topographic sur- 

 veys of the coastline and hydrographic sur- 

 veys of United States and Territorial waters. 

 This manual is intended to describe the field 

 operations required to accomplish hydro- 

 graphic surveys. Field methods and stand- 

 ards which are adequately described in other 

 Bureau manuals are not covered in this 

 manual except by appropriate references. 



The publication of an adequate series of 

 accurate nautical charts is undoubtedly the 

 Government's greatest single contribution to 

 safety at sea and the growth of the merchant 

 marine and other waterborne activities. 

 There are those who believe that hydrog- 

 raphers make a fetish of accuracy in sur- 

 vey operations, that many unnecessary re- 

 finements are attempted, and that some of 

 the final results are only "paper accuracies." 

 Few mariners attempt to evaluate a nautical 

 chart. They have a simple faith in its 

 accuracy. Where no dangers are shown they 

 believe that none exist. The hydrographer by 

 patient and relentless attention to every de- 

 tail must justify the mariner's boundless 

 confidence in his work. 



Fundamentally, hydrographic surveying is 

 that branch of physical oceanography em- 

 ployed to define the configuration of the 

 bottom of oceans and navigable waters of 

 lakes, rivers, and harbors. In a much 

 broader sense, the science embraces a wide 

 variety of activities, all of which are neces- 

 sary for compilation of nautical charts and 

 related publications designed to provide all 

 information required for safe navigation. 



1-2 Nautical charts. — The most impor- 

 tant criteria by which the value of a nau- 

 tical chart may be judged are its accuracy, 

 adequacy and clarity. A lack of any one 

 of these may result in a marine disaster 

 with consequent loss of life and property. 



Except for blunders in compilation, accuracy 

 depends directly on the quality of field sur- 

 veys ; the hydrographer and cartographer are 

 equally responsible for the adequacy, but the 

 cartographer alone can embody clarity in a 

 chart. 



Accuracy of a nautical chart is dependent 

 on the accuracy and adequacy of the hydro- 

 graphic surveys from which it is compiled ; 

 it cannot be more accurate. The increasing 

 size and draft of merchant vessels, growth 

 of submarine activity, and recent develop- 

 ments in exploitation of submerged lands 

 are combining to make the standards for 

 hydrographic surveying ever more strict. In 

 recent years new surveying and navigational 

 equipment have been devised and former ones 

 developed to greater perfection. Hydrog- 

 raphers must be alert to keep abreast of 

 advancing electronic and other scientific de- 

 velopments which can be adapted to survey 

 uses. 



While the need for greater accuracy and de- 

 tail in the deeper waters is becoming more and 

 more apparent, so too is the need for greater 

 attention to the inshore details and areas of shal- 

 low depths. The number of small boats in use 

 has gi'own enormously, giving rise to an un- 

 precedented interest in all manner of areas being 

 explored by these part-time mariners, areas that 

 were formerly of relatively little interest. 



Hydrographic field parties should be alert, to 

 every opportunity for field-checking the charts, 

 bearing in mind the requirements of every type 

 of chart user, from small boat to supertanker to 

 submarine. Evei-y instance where an improve- 

 ment can be made should be reported, supported 

 if possible by sufficient information to effect the 

 improvement. Of all chart users, hydrogi'aphic 

 parties are unique in their opportunity and 

 ability, not only to judge the accuracy and 

 clarity of our nautical charts but also to take 

 effective steps toward improvements. 



1-3 SPECIFICATIONS FOR HYDRO- 

 GRAPHIC SURVEYS.— This part, of the man- 

 ual summarizes general specifications for hy- 

 drographic surveys. Detailed discussion of 

 individual subjects will be found in later parts 

 of this manual or in other C&GS manuals. 



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