204 



HYDROGRAPHIC MANUAL 



Station names should never be placed in 

 the water area if it is possible to avoid it; 

 however, an unimportant sounding, espe- 

 cially in flat areas, may be omitted to pro- 

 vide space for lettering- if necessary. Where 

 there is room for only the hydrographic sig- 

 nal name, this is lettered and the full sta- 

 tion name together with the hydrographic 

 name is lettered in an unused part of the 

 sheet. Where the hydrographic detail is too 

 congested to permit these normal identifica- 

 tions, a capital letter (A, B, C, etc.) may 

 be used for reference to the full name placed 

 in an unused part of the sheet. Arrows can 

 be used to offset names and descriptions 

 provided they are not too long and do not 

 cross congested hydrography. The arrows 

 should be broken when they cross a sounding. 



6-16 Selection and use of pencils. — The 



use of proper drawing pencils is essential 

 for good drafting. Pencils which are too 

 hard may cut the surface of the paper, and 

 lines from such pencils are often too dim 

 to provide adequate photographic copy. The 

 point of a soft pencil soon becomes blunt 

 and often results in smearing the sheet with 



a layer of graphite which inhibits proper 

 penetration of ink into the surface of the 

 paper. Inked soundings deteriorate rapidly 

 on a graphite-coated sheet. 



A 3H or 4H pencil should be used for most 

 work on a smooth sheet. The degree of hard- 

 ness will vary as much as one grade in differ- 

 ent brands of pencils but is usually consist- 

 ent in each brand. Chisel-edged 5H pencils 

 should be used for constructing the projec- 

 tion and for plotting triangulation sta- 

 tions by lightly drawing intersecting dm. 

 and dp. lines. A hard chisel-edged pencil 

 should not be used to delineate the sounding 

 line as a guide for plotting soundings. No 

 pencil line should be drawn so firmly that a 

 permanent indentation is made in the paper 

 because this may result in rupturing the 

 sheet at the most critical places. Considera- 

 tion should be given to variations in the sur- 

 face of the paper caused by variations in 

 humidity. See Table 13 for schedule of pen- 

 ciled and inked details on a smooth sheet. 



6-17 Selection and use of ink. — The 



work of inking the survey properly is im- 

 portant. When completed it is the permanent 



Table 13. — Schedule of penciled and inked details 



Projection and geographic values 



Triangulation and topographic control symbols and names . . . 



Hydrographic control symbols and names 



Stations transferred directly from aerial photographs, and names 



Circle lines-of-control 



Completion of Stamp No. 42 



Landmark symbols and names 



Descriptive notes at stations and topographic features .... 



except at aids to navigation 



Tide and current stations 



Shoreline from final or advance manuscript 



Shoreline revised by hydrographer 



Low-water line from topographic survey 



Limit lines of foul areas, breakers, kelp, etc 



Ledge and reef 



Rocks and their elevations 



Aids to navigation not used as stations 



Hydrographic position identifications 



Lines connecting hydrographic positions 



Soundings 



Depth curves (Tables 3 & 4) 



Bottom characteristics 



Marine vegetation of any kind 



Other hydrographic features — piles, stakes, wrecks, etc 



Geographic names 



Junctions 



Wire-drag soundings (after Review) 



Data from prior surveys (after Review) 



(a) Ink black where unaffected by hydrography. 



Smooth plot 



Black 



After office 

 verification 



red. 



Selected colors. 

 Green. 

 Selected colors. 



