74 NAUTICAL CHART MANUAL 



VI 



Bottom Characteristics 



BOTTOM CHAEACTERISTICS (S) 



Bottom characteristics shall be spaced at reasonable intervals over the chart and shall be 

 placed a little below and to one side of the sounding. Within practical limits the representa- 

 tion should show the type of bottom on the different bottom features. Rocky areas unsuitable 

 for anchoring as weU as areas well suited for anchoring are of special interest to the navigator. 

 Fishermen have a special interest in the characteristics on shoals and those revealing areas in 

 which nets might be damaged. 



In general, two words or their abbreviations will suffice in describing bottom characteristics. 

 The abbreviations used must conform with those printed in the standard note on the chart. 

 Only in special cases will it be necessary to use any others. 



In harbors, inland waters, and along the coast, where the navigator may be interested in 

 the holding quality of the bottom, characteristics should consist of the type or character, such 

 as rky, hrd, M, sft, S, stk. Avoid hrd M and sft S. 



In deep water, characteristics should consist of the type of bottom, and color, if pertinent, 

 such as bk M, yl CI, Sh, S. 



VII 



Verification of Wire-Drag Surveys 



The area and depth diagram, which is also known as the "A and D sheet", shows the final 

 results of drag operations in a simplified and clear manner. It shows the maximiun effective 

 wire-drag depths in every portion of the area covered by the wire-drag survey. It also shows 

 the soundings as well as the groundings on shoals. A summary of groundings and clearances 

 is given in the Descriptive Report. 



The soundings and groundings are shown by black numerals; the groundings are encircled 

 in green ink. Notes at groundings give the maximum effective wire-drag depth at which the 

 groundings were cleared. If the grounding was not cleared by a subsequent wire-drag strip, 

 these notes will so state. 



A grounding not cleared by a wire-drag strip may be charted only as a sounding. Areas 

 shown on the A and D sheet as "splits" or insufficient overlaps of adjoining wire-drag strips are 

 considered not to be covered by the wire-drag. (For further information concerning wire-drag 

 surveys, see Coast and Geodetic Survey "Wire Drag Manual," pubUcation No. 20-1.) 



