6. THE SMOOTH SHEET 



207 



in the sounding records (see 4-37). When 

 a new name is used for a previously named 

 station, or an entirely different name is arbi- 

 trarily used to identify a triangulation sta- 

 tion used in hydrography, the new or arbi- 

 trary name shall be inked in blue, followed 

 by prior name or triangulation station name 

 in the color appropriate to the method of 

 location and in parentheses. If part of the 

 prior name is used, then that part shall be 

 underlined with the station color (Fig. 79). 

 Names of all control stations shall be inked 

 in capital letters 3 mm high having a line 

 weight of not more than 0.5 mm. The Leroy 

 lettering template No. 120C, with pen No. 00, 

 is suitable for this purpose. The year of 

 establishment shall be included for all tri- 

 angulation and traverse stations and for all 

 marked topographic stations or where, for 

 other reasons, the date of establishment is 

 noted on the photogrammetric survey. 



6-25 Vertical datums. — Hydrographic 

 survey data compiled by the Coast and Ge- 

 odetic Survey are referenced to three tidal 

 planes or datums. The sounding datum, or 

 zero depth, for the coastal areas of the At- 

 lantic Ocean and Gulf of Mexico is mean 

 low water (MLW). For Pacific Ocean areas 

 the datum is mean lower low water (MLLW). 

 In all areas the elevations of topographic 

 features are referred to the plane of mean 

 high water (MHW) which is represented 

 by the shoreline on the smooth sheet. Under- 

 lined elevations of mountain peaks are ref- 

 erenced to mean sea level. Local datums, such 

 as the Columbia River Datum or a specified 

 lake level, are used for certain of the larger 

 navigable rivers and lakes (see 1-45). 



6—26 Transfer of topographic detail. — 



The shoreline and all topographic details in 

 the water area shall be carefully transferred 

 to the smooth sheet for all inshore surveys. 

 Topography shall generally be omitted from 

 offshore surveys particularly where scale dif- 

 ferences are involved. As a general rule, 

 only contemporary photogrammetric or reg- 

 istered planetable surveys shall be used for 

 transfer of shoreline. Only advance or final 

 manuscripts shall be used when transferring 



shoreline and topographic detail from photo- 

 grammetric compilations (see 4-13, 14, and 

 15). Although the smooth sheet is not the 

 authority for shoreline in nautical charting, 

 the delineation of this and other details 

 should be accurate, as copies of the survey 

 are frequently furnished to individuals who 

 are not aware of this fact. 



The transfer may be made by burnishing 

 reverse blueline prints of the photogram- 

 metric manuscripts furnished at the scale 

 of the survey. If the information is fur- 

 nished in the form of a film positive, the 

 reverse side can be coated with blue Dry- 

 Rite ink and the transfer made by tracing 

 the detail with a stylus or hard pencil. In 

 each case it is necessary to make adjust- 

 ments for any differences in the two projec- 

 tions. Transfers of shoreline from plane- 

 table sheets shall be made by tracing paper 

 copy of the original. 



If final shoreline data are not available at 

 the time smooth plotting is started, the Wash- 

 ington Office shall be notified. The limits of 

 the area and the estimated date of completing 

 the processing shall be stated. No inshore 

 smooth sheet shall be forwarded to the office 

 without shoreline unless specifically author- 

 ized by the Director. 



6-27 Inking shoreline. — The transfer of 

 shoreline and topographic detail shall be 

 carefully checked before any part of it is 

 inked. The shoreline, specifically, the mean 

 high-water line shall then be inked with a 

 solid black line about 0.4 mm wide (Fig. 

 79). The shoreline of marsh, swamp, or 

 mangrove areas shall be shown by a fine 

 solid black line about 0.2 mm wide. The 

 outlines of small details of waterfront areas, 

 such as piers and bulkheads shall be shown 

 by moderately fine black lines. Sections of 

 shoreline shown on advance manuscripts by 

 dashed or broken lines shall be left in pencil. 



The shoreline shall not be generalized or 

 smoothed. Topographic detail shall never 

 obscure the control station point (Fig. 80). 

 The detail can usually be omitted within the 

 station symbol and only important features 

 or delineations within a symbol should be 

 shown with a fine line. Shapes of islets 



