6. THE SMOOTH SHEET 



225 



and otherwise undelineated channels and 

 depressions. The deeper supplemental curves 

 should be added only when irregular con- 

 figurations of the bottom warrant their ap- 

 plication. It is occasionally desirable to 

 emphasize a shoal which is not delineated by 

 any of the specified curves. A short-dash 

 curve may then be drawn after verification 

 of the survey. In inking this line it shall be 

 the color of the shoaler curve if the de- 

 lineated depth is only one unit deeper, such 

 as 19 feet versus 18. Otherwise, the curve 

 shall be brown and shall be inked as a solid 

 line. 



Where the curves become congested or con- 

 fusing on steep slopes, the shoalest and deep- 

 est curves should be shown and the inter- 

 mediate curves omitted. The shoalest curves 

 which mark hazards to navigation and the 

 deepest which mark the limits of channels 

 or passages are most important. Where 

 rocks or steep shoals rise abruptly from 

 much greater depths one or more of the 

 deeper curves should be omitted. Where is- 

 lands, shoals, or reefs rise abruptly from 

 much greater depths and several of the 

 shoaler depth curves are very close to the 

 shorelines of the islands, or edges of the 

 reefs, the shoaler curves should be omitted. 



The low-water line, the curve of zero depth, 

 is an important foreshore feature and in 

 some places is an important waterfront 

 boundary. Particular care shall be taken in 

 the delineation of this line. Inasmuch as 

 it may be surveyed on both hydrographic 

 and topographic surveys it is necessary to 

 select the line to be shown on the hydro- 

 graphic survey. Criteria are specified in 

 6-28. 



6-65 Floating aids to navigation. — All 

 aids to navigation within the area surveyed 

 shall be shown on the smooth sheet. Floating 

 aids shall be indicated by the appropriate 

 aid symbol in pencil and will be inked in the 

 proper color after verification (Fig. 79). The 

 dot of the buoy symbol and the small circle 

 of the lightship symbol shall be placed at 

 the hydrographic position. Soundings at 

 these aids are usually plotted slightly lower 



and out of position in order not to overlap 

 the symbols. 



Each aid shall be identified by name, clas- 

 sification, or number as "N7" or "BELL" 

 and should be in agreement with charted 

 and Light List designations. Any discrep- 

 ancy in designation, description, or char- 

 acteristic noted during the survey should be 

 mentioned in the descriptive report. 



6-66 Miscellaneous data. — In addition to 

 the routine data plotted on each smooth 

 sheet there may be various other important 

 data to be plotted. These data may be re- 

 corded in the sounding volume or supple- 

 mental record book, on the boat sheet, or on 

 the fathogram. They are individually dis- 

 cussed in the following sections. 



6-67 Wrecks. — Stranded wrecks where 

 part of the hull uncovers at low water are 

 frequently transferred to the smooth sheet 

 from topographic surveys, usually where a 

 hulk is stranded near the shoreline (Fig. 79). 

 The small circle of the symbol is the position 

 of the wreck. These wrecks might postdate 

 the topographic survey and be located by 

 detached position, by reference to a sound- 

 ing line, or spotted on the boat sheet. Some- 

 times large hulks are outlined and labeled 

 on large-scale surveys. 



Sunken wrecks are covered at low water, 

 except that the masts may uncover. In such 

 event the notation "masts" shall accompany 

 the sunken-wreck symbol. Sunken wrecks 

 are located at detached positions, and when 

 the least depth is obtained it is plotted with 

 notation "wreck" instead of the symbol. Off- 

 shore sunken wrecks are usually located on 

 wire-drag surveys, and the least depths or 

 groundings are transferred to the smooth 

 sheet in green ink after office verification of 

 both surveys. 



6-68 Wire drag finds and clearances. — 



Where a wire-drag examination has been 

 made by the hydrographic party to deter- 

 mine the least depth on a shoal or obstruc- 

 tion, the least depth found (if less than that 

 of the hydrographic survey) shall be plotted 

 in pencil, and a note with a leader added 

 giving the least depth with position number 



