916 HYDROGEAPHIC MANUAL PaGE 826 



Points shall be used only to indicate approximate or general directions. A table is included in the 

 appendix of each Pilot for conversion of true directions in degrees to equivalent magnetic directions in 

 points. (See Magnetic courses and bearings.) 



Avoid so far as possible referencing courses to floating aids to navigation, such as buoys. If 

 possible, refer them to some fixed prominent object, that is unmistakable, easily identified, and 

 permanent. 



Give danger bearings where important. Give bearings of ranges and channels. 



Bearings to clear offshore dangers, etc., are given from seaward, but to locate offshore dangers 

 or objects, they are given from landward. Light sectors are defined by giving bearings from seaward. 



BLUEPRINTS AND MAPS OBTAINED LOCALLY.— From the U. S. Corps of Engineers and 

 local authorities, such as State, county, or town engineers, it is often possible to obtain blueprints of 

 surveys, and maps of harbors showing changes that affect the charts, as well as the Coast Pilots. This 

 should be done where possible. It should be borne in mind, however, that such data, to be of value 

 for correlation with existing surveys and charts of the Bureau, must be connected with the federal 

 network of triangulation. Three well-distributed points, so connected, wiU ordinarily provide excel- 

 lent control (see 2361). For use in Coast Pilot revision only, such accuracy is not required, and the 

 reviser should use his judgment as to what is needed. 



A personal inspection of the area will generally be required to ensure that the map or blueprint 

 shows actual conditions. State on the print whether this was done and note existing conditions 

 plainly. (See 2361 and 834.) 



Many blueprints of surveys by the U. S. Corps of Engineers and other organizations are on 

 file in the Office. Depths in channels and at wharves can often be found on these. Maps of harbors 

 are sometimes made by local interests and copies may be available. 



BONDED WAREHOUSES.— If available, describe facilities. 



BOTTOM, CHARACTER OF.— (See Soundings.) 



BOUNDARIES. — National or State boundaries should not be mentioned because of possible 

 complications. Boundary monuments are sometimes landmarks and may be described as such. 

 If information about boundaries is required, refer to U. S. Geological Survey Bulletin No. 817. 



BOUNDARIES OF INLAND WATERS.— These are given in the "Rules of the Road," which 

 are issued free of charge by the U. S. Coast Guard. They are not to be published in the Coast 

 Pilots. (See Rules of the Road.) 



BREAKERS. — Give location, limits, and stage of tide and weather conditions at which they 

 break. State whether the rock or reef bares, how much, and at what stage of tide. (See Bars.) 



BRIDGES. — Bridge data should be included in a table in the appendix. This table should 

 include all bridges over navigable waters in the region, together with information that can be tabu- 

 lated, such as, type of bridge, prescribed signal for opening, horizontal and vertical clearances at mean 

 high water, which side of draw or bridge opening should be used, and depth of water below bridge, if 

 pertinent. Bridge data for the most important ports, in which there may be a number of bridges, 

 may be included in a table in the text where the port is described. These latter bridges should not 

 be duplicated in the appendix, but reference should be made to the page of the text where they may 

 be found. 



Any necessary rules and regulations governing the operation of bridges should be included in 

 the text. The reviser should obtain copies of such rules and regulations. It is essential that the Coast 

 Pilot contain enough details to enable the mariner to make full use of the channel through the bridge, 

 but details of no value to the mariner should be omitted. 



Where there are a number of bridges in the same locality there will probably be enough of the 

 regulations common to all or nearly all of these bridges, so that these regulations can be grouped and 

 printed only once, noting the necessary exceptions. 



Information regarding bridges can be obtained from two volumes, both published by the U. S. 

 Corps of Engineers, which has jurisdiction over the construction and operation of bridges over navi- 

 gable waters of the United States. One volume, "Rules and Regulations Relating to the Navigable 

 Waters of the LTnited States," contains the rules for operation of most of the bridges; and the other, 

 "List of Bridges over Navigable Waters of the United States," gives the dimensions of the openings 

 and other data. Copies of these, corrected to date, should be obtained. The U. S. Corps of Engineers 

 is the authority for information regarding bridges, and where there is a discrepancy between data 

 obtained in the field and those contained in these publications, the safer of the two should be used. 



The reviser should make certain, while still in the field, that the necessary information for each 



