772 



HYDROGRAPHIC MANUAL 



Page 718 



It is obvious that it may bo nocossary to convert from the unit on the smooth sheet 

 to another unit for charting purposes and this shall be done in accordance with the fol- 

 lowing rules (see also fig. 162): 



(1) Where the charted soundings are to be in the same integral unit used on the smooth sheet the 

 soundings shall be transferred without change. 



(2) Where a sounding in feet on the smooth sheet includes a fraction, the fraction shall be omitted 

 in charting (e. g. 8J^ feet = 8 feet). 



(3) Where the soundings on the smooth sheet are in integral feet and are to be charted in fathoms 

 and quarters, fathoms and half fathoms, or integral fathoms, the odd feet shall be converted as follows: 



(4) Where the soundings on the smooth sheet are in fathoms and tenths and a:-e to be charted 

 in integral feet, integral fathoms, fathoms and quarters, or fathoms and half fathoms, the decimals of 

 fathoms shall be converted as follows: 



772. Plotting the Soundings 



To avoid soiling tlie smooth sheet during the penciling or inking of the soundings, 

 it should be kept completely covered, except for the small area actually being worked 

 on. A convenient method is to use a large piece of celluloid about 2}^ feet square with, 

 a circular, hole, 3 to 4 inches in diameter, cut in its center, the celluloid being moved 

 around as necessary during the work. Paper can be used instead of celluloid, but cellu- 

 loid has the advantage of permitting the work to be seen through it. Other parts of 

 the sheet can be kept covered with convenient sized pieces of obsolete charts or wrap- 

 ping paper. (See 731.) 



The plotting of the soundings on the smooth sheet follows generally the same pro- 

 cedure used in plotting the positions; that is, the plotter usually begins with position 

 1 of "A" day and plots the soundings in the order in which they were actually taken 

 in the field. This procedure is, of course, not a requirement, and it may be advanta- 

 geous to depart from it in specio-l cases. 



All soundings that are penciled or inked on the smooth sheet shall be spaced ac- 

 cording to the recorded time, or the travel of the paper in the case of fathograms, 

 and spacing dividers (see 4813) shall always be used for this purpose. No deviation 



