Page 195 hydrogeaphy 3132 



most recent periodic survey. In a nonchangeable area, a contemporary survey by such 

 an organization shall not be duplicated, if a suitable agreement in depths is reached at 

 the junctions, irrespective of whether the survey is periodically repeated. 



3132. Survey Overlap at Junctions 



An overlap of at least one sounding line shall be made with an adjacent survey 

 except as provided in 3133, and if the depths at the junction are not in agreement, 

 the new survey shall be extended into the old until a satisfactory agreement has been 

 reached. If a reasonable extension into the other survey discloses no tendency toward 

 an agreement, an investigation shall be made to determine the reason therefor and 

 a report of the investigation and the conclusions reached made to the Washington 

 Office with a request for further instructions. All details of such investigations should 

 be included in the Descriptive Report. 



The overlap specified herein shall apply to the following classes of surveys: 



(a) All noncontemporary surveys. 



(b) Contemporary surveys by a different survey party. 



(c) Contemporary surveys of the same party made in different years; by different methods; or 

 from different vessels, as the survey vessel and one of her launches. 



(d) Surveys by other organizations. 



3133. Junctions With Contemporary Surveys 



Where the hydrographic survey is contmuous in the same year, by the same 

 method and from the same survey vessel, junctions between adjacent sheets may be 

 made by spacing the hydrography just as it would have been spaced had the two been 

 combined on one sheet. Any discrepancies in the depths or the depth cm-ves at the 

 jimctions shall be investigated and corrected before leaving the field, as is required for 

 discrepancies between any two adjacent lines of a survey. 



314. Systems of Sounding Lines 



For a hydrographic survey of an area a methodical and systematic examination is 

 the principal requirement of any system of sounding lines adopted. A system must 

 be chosen that will develop the area and delineate the submarine relief in the most 

 thorough and economic manner, and a series of evenly spaced sounding lines is the best 

 method yet devised to accomplish this. The purpose of the regular systems of lines is: 

 first, to furnish a realistic representation of the sea bottom and the submarine relief; 

 and second, to reveal mdications of shoals or dangers which are subsequently investigated 

 for least depths. 



The project instructions ordinarily specify in a general way the direction of the 

 principal system of lines, but in parts of a project the preferred direction often depends 

 on local conditions where the Chief of Party or the hydrographer is expected to use 

 his judgment. 



In general, a system of evenly spaced lines approximately parallel to one another 

 and normal to the depth curves will provide the most convenient and economic develop- 

 ment of an open coastal area, but it is frequently more advantageous to adopt some 

 other system because of the location of the control, or the distribution of convenient 

 anchorages or shore bases. The system adopted for the open coast is not necessarily 

 also suitable for bays and harbors. For the development of steep features, however, 



