HTDROGRAPnT 75 



VIII 

 Review of Hydrographic Surveys 



The written review appended to the Descriptive Report of a hydrographic survey is a 

 record of the discussions, evaluations, and recommendations derived from a comprehensive 

 study of the latest and prior surveys by this Bureau and charted information from other sources. 



The compiler shall read the review before applying the survey to a chart. The review 

 serves as an important aid to the compiler in the construction or revision of a nautical chart. 



A review's main purpose is to make the new survey complete with reference to all informa- 

 tion on prior hydrographic or wire-drag surveys so that it is unnecessary for the chart compiler 

 to consult any prior surveys of the area covered, except as specifically mentioned in the written 

 review. The latest reviewed basic survey supersedes all prior surveys in the common area. 

 In order to do this, it is frequently necessary to carry forward from the prior surveys to the 

 present survey, data which have not been confirmed or disproved by the present survey. 



Compilers vsdU find specific comments and conclusions in the review relative to the char- 

 acter, of the area, shoreline, and development of the bottom f eatm-es including the least depths 

 on shoals or obstructions. The adequacy of the junctions with contemporary surveys or other 

 currently charted detail is considered and evaluated. 



Discussions by the reviewer, under "Comparison with prior surveys", consider changes in 

 shoreline or bottom configuration and state whether these changes are due to natural or arti- 

 ficial causes or to less detailed and accurate methods employed in the prior surveys. 



Under the heading "Comparison with, chart" the origin of the charted data is Usted, and 

 all difiFerences between the charted and current siu-vey data are enimierated. The majority of 

 the charted information will have been considered in the comparison with prior surveys. 

 Therefore, attention need be given only to the charted data from Chart Letters, advance 

 copies of Boat Sheets, Coast Guard and Naval Oceanographic OfEce Notices to Mariners, 

 Corps of Engineers surveys, or other sources. Where charted data from sources other than 

 the Bureau surveys have not been disproved by the present survey and should be retained on 

 the chart, a specific recommendation to that effect is made. Finally the discussion is concluded 

 with a statement as to the adequacy of the present survey to supersede the charted hydrography. 



In cases where improved channels fall within the area of the hydrographic survey, the 

 controlling depth notes are usually furnished by the Corps of Engineers. Controlling depth 

 notes dated subsequent to the present sirrvey information are recommended for retention on 

 the chart. 



Where shoals and channels have shifted in position and are not adequately marked by the 

 charted buoys, or a new unmarked danger is noted, the review wiU so state. Differences 

 between the charted and present survey position of the fixed aids to navigation are noted. 



The compiler should note whether or not the survey and review has been finally inspected 

 and approved for application to the charts or if it has been previously partially appHed. Guid- 

 ance as to the proper procedure should be sought from the Chiefs of the Conventional or 

 Small-craft Chart Branches. 



Finally the compiler should give reasons in the "History of Cartographic Work" for devia- 

 tions, if any, from the recommendations made under "Comparison with charts" in the review. 



