Page 207 hydrography 3233 



graphic survey. Where this is not the case, the shoreline may be omitted if its transfer 

 presents difficulties (see 751). In such case, however, the Descriptive Report shall 

 include a statement that the usual verification of the shoreline and topographic details 

 was omitted, and the reason therefor. 



On hydrographic surveys which do not extend close to shore, the shoreline may 

 be omitted entirely, or it may be generalized on the boat sheet if its representation is 

 considered desirable by the hydrographer. 



3233. Soundings at Junctions 



To ensure satisfactory junctions in coverage and depths with adjacent surveys, 

 the soundings at the limits of the latter shall be transferred to the boat sheet before 

 starting a hydrographic survey. These soundings shall appear in colored ink, prefer- 

 ably red, to distinguish them from soundings taken during the survey. Soundings 

 thus transferred may be from prior surveys with which a satisfactory junction is to be 

 made as specified by the project instructions, or they may be from hydrographic 

 surveys currently made, either at the same or different scales. 



3234. Data From Prior Surveys 



All dangers to navigation, including the least depths on all shoals, shall be trans- 

 ferred to the boat sheet from photographic copies of prior surveys in the area, if 

 available. If such copies are not available, these data shall be transferred from the 

 largest-scale chart of the area. In addition to least depths and other dangers, it is 

 desirable to transfer representative soundings and depth curves from the prior 

 surveys. All data transferred from prior surveys shall be in a distinctive color, 

 preferably red. 



It is required that the dangers, shoals, and least depths on them be definitely 

 proved or disproved during the new survey. Comparison with the other transferred 

 data provides a check as the survey progresses. The depth curves are especially helpful, 

 as they enable the hydrographer to warn the leadsman or the fathometer attendant of 

 expected changes in depth. 



3235. Data From Published Charts 



After the data mejitioned in 3234 have been transferred to the boat sheet, it must be 

 compared with a new print of the largest-scale chart of the area, and any additional 

 dangers on the latter transferred to the boat sheet. The printed chart frequently 

 contains later data or data derived from other sources. 



3236. Reported Shoals and Dangers 



In addition to known shoals and dangers, the positions of any reported menaces 

 to navigation, which have not been charted, shall be plotted on the boat sheet, with 

 suitable notes, so that their positions may be accurately determined or their existence 

 disproved. Some of these reported dangers may be specifically mentioned in the 

 project instructions; others may be reported locally to members of the survey party. 



3237. Other Details 



Since the boat sheet is the hydrographer's work sheet, other details which are 

 considered of possible use during the survey may be shown. Of advantage in certain 

 types of surveys are a large compass rose and one of the several different types of 



