112 NAUTICAL CHAKT MANUAL 



RECENT DEVELOPMENTS 



I 



Bathymetric Compilations 



SPECIFICATIONS ADOPTED FOR IHB PLOTTING SHEETS 



U.S. Naval Oceanographic Office "3000 Series" Plotting sheets shall be used for compila- 

 tion bases. Negatives of this series are obtained from the Naval Oceanographic Office on 

 written request. From these negatives three blackline prints are made on matte finish plastic, 

 to be used as follows: (1) Primary Compilation — for sounding data corrected to true depths — 

 shown in upright type; (2) Secondary Compilation — for uncorrected or discrete sounding 

 data — in italic type;* (3) History Overlay — to show source of all sounding data. ^ 



*NOTE: Corrected and uncorrected soundings shall not appear on the same compilation. 



Soundings shall be in fathoms and shall be no larger than 2.00 mm. nor smaller than 

 1.50 mm. The position of the sounding shall normally be the center of the figures forming the 

 sounding. However, where close development requires, a dot with a dashed leader line con- 

 necting the sounding to the dot is permissible. A maximum number of soundings shall be 

 used except, there shall be a minimum of 1.00 mm. spacing between them. Soundings are 

 preferably oriented perpendicular to the parallels or, as a second choice, to the direction of the 

 sounding line. Both these preferences are waived when close development of significant 

 features is required. 



The required 100 fathom curve, and all depths shoreward of it, are to be taken from the 

 nautical charts of the affected area. Where other depth curves are used to facilitate compila- 

 tion they must be drawn in non-photographic blue ink. 



Other general requirements are : Plotting sheets are to be maintained (corrected) periodi- 

 cally by applying data received subsequent to completion of original compilation. Original 

 compilations and history overlays are to remain in the Coast and Geodetic Survey, with only 

 black-line prints on stable-base film positives to be furnished IHB on their request. Important 

 land geographic names may be shown, in upright type, if they do not encroach on the sea areas. 

 The only topogi-aphy to be shown is the HWL. The Coast and Geodetic Siu-vey plotting 

 sheets are basic. All prior (or current) IHB plotting sheets are to be used only as a reference 

 or to fill in areas not covered by Coast and Geodetic Survey or Naval Oceanographic Office 

 Surveys. 



