6. THE SMOOTH SHEET 



209 



added in pencil. These dashed pencil lines 

 shall be accompanied by an appropriate no- 

 tation as : "shoal," "foul," "breakers," "kelp," 

 etc., in pencil, and shall be inked in black 

 as necessary during office verification. 



Similarly, limits of other foul areas dis- 

 covered during the hydrographic survey 

 shall be defined by dashed pencil lines and 

 identifying notes which shall be inked in 

 black during verification. Usually these are 

 areas which cannot be sounded because of 

 undue risk of damage to the sounding ves- 

 sel (see 5-17). 



6-30 Ledges and reefs. — A ledge is a 

 rocky formation connected with and fring- 

 ing the shore and is generally above the 

 sounding datum in elevation. A reef is a 

 rocky or coral elevation dangerous to sur- 

 face navigation which may or may not be 

 above the sounding datum in elevation. A 

 rocky reef is always detached from the shore, 

 but a coral reef may or may not be con- 

 nected with the shore. 



Symbols for ledges and reefs (Fig. 79) 

 transferred from the topographic survey 

 shall not be inked until after the hydrog- 

 raphy is plotted and any conflicting delinea- 

 tion is resolved. If any differences between 

 the two surveys are not readily resolved, 

 then inking of the symbols should be de- 

 ferred until office verification. In the trans- 

 fer of very small, isolated reef patches the 

 rock-awash symbol shall be substituted for 

 the reef symbol. On the other hand, where 

 a cluster of closely grouped rock-awash sym- 

 bols extend over an appreciable area, the 

 reef symbol should be substituted. Ledges 

 and reefs shall not be transferred to the 

 smooth sheet in areas beyond the general 

 limit of hydrography if they are within 

 areas fully covered by adjoining surveys. 



Along continuous stretches of ledge or 

 reef, the symbol shall be substituted for zero 

 and minus soundings of general elevation 

 (see 6-35) when inking after office verifica- 

 tion. Care should be taken that this sym- 

 bolization is not extended through interven- 

 ing beaches. 



Care shall always be exercised where zero 

 soundings occur within an area of ledge or 



reef symbolization that they are not er- 

 roneously inked as bare rocks or islets. 



6-31 Bare rocks. — Bare rocks are those 

 extending above the plane of mean high wa- 

 ter. For smooth sheet work, and charting, 

 rocks with elevations of 2 feet or more above 

 mean high water on the Atlantic or Gulf 

 coasts, or 3 feet or more on the Pacific Coast, 

 shall be shown as bare rocks (Fig. 81). The 

 actual size and shape of the rock should be 

 shown if that is possible at the scale of the 

 survey. Otherwise, a small single rock should 

 be exaggerated in size and shown on the 

 smooth sheet with an open center. Where 

 there is a cluster of bare rocks shown by 

 dots on the topographic survey, then one or 

 more open-center symbols should be used. 

 The bare rock shall never be overlapped by 

 rock-awash or sunken-rock symbols. 



6-32 Rocks awash. — Rocks awash are 

 those exposed at any stage of the tide be- 

 tween mean high water and the sounding 

 datum, or that are exactly awash at these 

 planes. Rocks shall be represented on the 

 smooth sheet by the rock-awash symbol (Fig. 

 81) where their summits are in the zone 

 between 1 foot above mean high water and 

 1 foot below the sounding datum on the At- 

 lantic Coast. On the Pacific Coast the limits 

 are 2 feet. 



The symbol shall be drawn with bold neat 

 pen strokes. They shall not be reduced in 

 size where there is a congestion of other 

 rocks or soundings. No attempt should be 

 made to plot a symbol for each rock in a 

 closely grouped cluster of rocks. The num- 

 ber of symbols should be reduced to avoid 

 overlapping symbols. When suitable, the 

 reef symbol should be used. 



6-33 Sunken rocks. — Sunken rocks are 

 those covered at the sounding datum, that 

 are potentially dangerous to navigation. 

 For purposes of smooth plotting, and chart- 

 ing, rocks potentially dangerous to naviga- 

 tion, whose summits are below the lower 

 limit of the zone for rocks awash (see 6-32) , 

 are classed as sunken rocks and are repre- 

 sented on the smooth sheet by symbol (Fig. 

 81) or by a sounding accompanied by the 



