Page 851 miscellaneous 9334 



The character of the inked soundings shall be in accordance with the instructions 

 in 773. Soundings in fractions or decimals shall be in accordance with 7713 and 7714 

 and shall be inked in accordance with 7734, but which fractional soundings are to be 

 inked shall be decided at the time of verification. Minus soundings shall be inked 

 in accordance with 7715 and 7735. Special attention must be paid to ensure that the 

 least depth is plotted on all shoals and dangers, and in accordance with 7753. 



Where all recorded soundings cannot, or need not, be plotted, and where soundings 

 are taken from fathograms, selection shall be made in accordance with 7725 and 7726. 

 Where the somidmgs are from fathograms or where some of the soundings recorded in 

 the Sounding Records are omitted in the inking, a notation should be included in the 

 title on the sheet. 



a. Erroneous soundings. — These may be due to errors in the recorded depths, errors 

 in reducing the soundings, or the soundings may not be in their true positions. Owing 

 to the fact that there is little opportunity to check the various field operations as they 

 are performed, the verifier of the smooth sheet must watch for all abnormal soundings 

 which may constitute errors. Examples are: depth curves out of harmony with others 

 in the locality; bad crossings; shoal soundings where none should be expected; deep 

 soundings in shoal areas. 



The various causes of errors in recorded soundings are discussed in 774. The re- 

 duction of all suspicious soundmgs should be checked . Soundings taken with an inclined 

 leadline or wire are always too deep (see 3464). 



Discrepancies between the soundings of overlapping surveys, or where the area 

 is distant from the tide gage, may be due to erroneous tidal planes. Such cases should 

 be referred to the Division of Tides and Currents for re-examination. (See also 825.) 



b. Bottom characteristics. — Bottom characteristics shall always be inked, but it is 

 not always necessary to ink all that are recorded, and a judicious selection is required. 

 The bottom characteristics of outstanding shoals should always be shown. Where echo 

 sounding has been used, it may be necessary to carry bottom characteristics forward 

 from prior surveys (see 3842). The symbols of part "O" of the Symbols and Abbrevia- 

 tions chart (fig. 189) shall be used, and shown in accordance with 3843 and 783. 



9334. Topography, Rocks, and Shoal Areas 



The shoreline should always be shown on inshore surveys. It is desirable, although 

 not essential, to have the shoreline on offshore surveys. (See 751.) Shoreline revised 

 by the hydrographer or originating with the hydrographic survey should be inked in 

 accordance with 753. 



Contemporary topographic surveys are the source of the shoreline, most of the 

 control stations, and many of the rocks on hydrographic sheets. They should be ex- 

 amined for rocks, especially rocks awash, which may have been omitted or transferred 

 in error. Such of these as appear authentic should be placed on the sheet. The 

 topographic surveys are also the source for the low-water line where the hydrographic 

 survey fails to define it with zero soundings. The air photographic surveys should 

 also be examined when drawing low-water lines. The low-water lino shall be inked 

 in accordance with 754. 



Shoal areas that are covered at low water but that have not been sounded should 

 be outlined with a black dash line and appropriately marked. These occur infre- 

 quently. 



