114 HYDROGRAPHIC MANUAL PaGE 8 



but to survey even the precise details of form. In recent years submarine valleys along 

 the continental slopes which were only partly known or suspected have been disclosed 

 in surprising detail. 



The hydrographic surveys have an extremely interesting and important significance 

 for the geomorphologist; the submerged portions of the continental masses are being 

 slowly revealed, and a better understanding of that part of earth history hidden beneath 

 the sea is in prospect. 



114. The Hydrographic Manual 



This Manual is one of a series published by the Coast and Geodetic Survey to 

 describe the methods and equipment and to state the general requirements for the 

 various survey operations. As explained in 1132, hydrographic surveying is considered 

 to be only one phase of combined operations, for each phase of which there is a separate 

 manual. 



To avoid duplication, this Manual treats principally of the operation of sounding 

 and of the details of hydrographic surveying after a topographic survey has usually 

 been made and is available. It does include some important phases of other operations, 

 particularly as applicable to hydrographic surveying, and supplements other manuals 

 where the requirements have been changed. 



For combined operations each hydrographic survey party needs continually at 

 hand the following manuals, and frequently has use for many of the publications of the 

 Bureau listed in 952: 

 Special publications , 



No. 118. Construction and Operation of the Wire Drag and Sweep. 

 No. 144. Topographic Manual. 



No. 145. Manual of Second- and Third-Order Triangulation and Traverse. 

 No. 196. Manual of Tide Observations. 

 No. 215. Manual of Current Observations. 

 Serial No. 166. Directions for Magnetic Measurements. 



It should be noted that in this Manual the expression "hydrographic surveying" 

 is almost always used in its limited sense, to refer to operations described in 1132, 

 although occasionally it may be used in the broad sense to include combined operations. 

 Likewise, the term "hydrographer," as used, almost invariably refers to the officer in 

 immediate charge of the hydrographic survey unit. For a survey ship, the hydrog- 

 rapher is, of course, the Commanding Officer; but for smaller units, the officer responsible 

 for the daily operations of the unit, even though only temporarily assigned to such duty, 

 is the hydrographer. 



12. PROJECT 



The field operations of a hydrographic survey in a specified area are considered a 

 project, and to each project is assigned a number such as CS-253, the letters being the 

 abbreviation for Coastal Surveys. Former numbers of the series were preceded by the 

 initials HT-, which stood for Hydrography and Topography. 



Each project is considered a "project of combined operations," since contem- 

 porary surveys of other types are usually required in connection with the hydrographic 

 surveys in any area. 



A project may consist of two or more minor surveys of a similar type in nearby 

 areas even though the areas are not adjoining. The size of any one project is such 



