142 



HYDROGRAPHIC MANUAL 



(a) Where the horizontal axis of the nu- 

 meral approximately parallels the direction 

 of the sounding line, 1-digit numerals should 

 be spaced about 6 to an inch, 2-digit nu- 

 merals about 4 to an inch, and 3-digit 

 numerals about 3 to an inch. 



(b) Where the horizontal axis of the nu- 

 merals is approximately normal to the di- 

 rection of the sounding line, numerals 

 should be spaced 3 to 6 to the inch depending 

 on the depth. 



(c) Where numerous decimals or frac- 

 tions are to be shown these may be consid- 

 ered as equivalent in width to about one 

 half digit. 



With these rules as a guide, the hydrog- 

 rapher should select a sounding interval 

 which, when the soundings have been plotted, 

 will accurately portray the bottom configura- 

 tion. The recording of an excessive number 

 of soundings is wasted effort, and the waste 

 is compounded in every phase of subsequent 

 processing, verification, and inking (see 

 6-59). 



5-30 Depth units. — The depth units to 

 be used in various %reas and depths are 

 specified in Section 1-38 and Table 2. Sound- 

 ings shall always be recorded in fathoms and 

 decimals, or feet and decimals; fractions 

 shall never be used. Ocassionally it is advis- 

 able to record soundings in fathoms in part 

 of the area being surveyed and in feet in 

 other parts. The record should indicate 

 which unit is being used (see 5-95). Only 

 one unit, feet or fathoms, shall be used 

 when plotting soundings on the boat sheet. 



5-31 Fathograms. — The graphic record- 

 ing of a bottom profile produced by any type 

 of echo sounder is called a fathogram. The 

 profile must be correlated with other recorded 

 data. Stamp No. 31, Graphic Record, is used 

 for this purpose (Fig. 55). The stamp shall 

 be impressed at each end of the fathogram 

 and the required information entered in all 

 spaces. 



Each echo sounder is provided with a fix 

 marker button, which, when pressed, will 

 cause the stylus to draw a line across the 

 paper. At each fixed position along a sound- 



No. 31 GRAPHIC RECORD 



Sheet NoMt^.e-^1^ Recorder No._^^ 



\.oa\\\>i.2jAxfJi.^cuth.Shee<L 



Vessel --/..d<//?£>b__M2_v5- 



From Pes. No. - _ /t! Date i>-J-'t :£Ji 



To Pos. No. _ _ /_7ii tl Date ^rJH r^9. 



Jagged profile (not) caused by seas. 



U'-B^-Cpi&n Operator 



Tide reducers by Ctiecked by: 



Figure 55. — Stamp used to identify fathograms. 



ing line and at each detached position where 

 a sounding is recorded, the echo sounder 

 operator shall make a fix mark, and the 

 position number shall be shown beside it. 

 When a fix is rejected or missed, the fact 

 shall be indicated by one or more crosses on 

 the fix mark. The day letter should be shown 

 at intervals of about 10 positions (see 5-55). 



In order that the fathogram may be pro- 

 perly related to the hydrography, the opera- 

 tor shall make notes on the record to indicate 

 where a line begins, turns, ends, or breaks. 



Each echo sounder records depths in more 

 than one phase depending on its design. The 

 EDO 255 and 808 type recorders have four 

 phases and record on paper which has four 

 scales. The first, or A phase is always identi- 

 fied by the initial trace, but all other phases 

 must be identified by notes on the fathogram 

 and in the record book. Each change of phase 

 must be noted and recorded and the phase in 

 use indicated on the fathogram. A circle can 

 be drawn around the number at the top of the 

 scale being used, or a note may be written 

 on the fathogram to indicate each change 

 of phase. 



When the EDO-185 is being used with 

 more than one stylus, the fathogram must be 

 marked "^600" when the second stylus is 

 recording the depth, or "+1200" when the 

 third stylus is recording (see 3-79). 



The Precision Depth Recorder (PDR) re- 

 cords in 400-fathom phases automatically. 

 It is important that each phase be identified. 

 The initial trace will be recorded as on 

 other types of fathograms, however, there is 

 no printed scale and all soundings are re- 



