Page 211 hydrography 3255 



in 3533. Depth curves should be drawn daily and revised daily to conform with the 

 more complete information available. All depth curves should be left in pencil until 

 it is certain that no further revision will be required. As the various parts of the area 

 are completely surveyed, the curves should be inked, using the standard colors from 

 table 27 in 776 insofar as they are applicable. 



3255. Notes 



Use of copious penciled notes on the boat sheet is permitted and encouraged; for 

 example, those made along the margin to remind the hydrographer of the need for 

 additional development or data before leaving the field. Others are of assistance to 

 the hydrographer in preparmg the Descriptive Report, and to the smooth plotter in 

 his interpretation of the Sounding Records and other data. Facetious and useless 

 comments should, of course, not be included in such notes. (See 7912.) 



All notes that are of permanent value and that contain information that should 

 be transferred to the smooth sheet shall be inked before the boat sheet is transmitted 

 to the Washington Office. Those that will serve as directions or explanations to the 

 smooth-sheet plotter may be left in pencil. All temporary notes and symbols for the 

 hydrographer' s temporary use only should be erased. 



Wliere it has been impossible to survey over a shoal area because of heavy tide 

 rips or breakers, which occur even in moderate weather, the area should be outlined 

 on the boat sheet with a broken line in black ink, with an appropriate note explaining 

 why the area was not sounded and giving an estimate of the least depth. 



3256. Junctions With Other Surveys 



The approximate limits of adjoining surveys shall be shown on the boat sheet by 

 inked lines in a distinctive color, accompanied by the registry or field numbers of the 

 adjoining surveys (see 788). 



3257. Review of Completed Sheet 



After the field work of a hydrographic survey has been completed, and before the 

 records leave his custody, the hydrographer should make a thorough examination and 

 review of the boat sheet to ensure that all details of permanent value have been inked, 

 and that they are unmistakably clear and legible. The use which is to be made of the 

 boat sheet by the smooth plotter and in the Washington Office should be borne in mind. 

 (See 3211 and 3212.) 



326. Shipment of Boat Sheet 



The boat sheet shall always accompany the smooth sheet whenever the latter is 

 transmitted to any other party. Processing Office, or the Washington Office. It shall 

 be forwarded, however, in a separate package and at a different t me from the smooth 

 sheet and the Sounding Records. Shipment may be made by registered mail or by 

 express. A transmitting letter (Form No. 413), in duplicate, shall be mai ed sepa- 

 rately. A triplicate of the transmitting letter shall be included in each package. For 

 further details of shipments see 836. 



33. HORIZONTAL CONTROL OF HYDROGRAPHY 



A hydrographic survey is a three-dimensional survey in which a sounding repre- 

 sents a vertical measurement of the depth of the water, which must be located in the 

 horizontal plane by two coordinates. Obviously a knowledge of the depth is useless 



