148 



HYDROGRAPHIC MANUAL 



be recorded at regular intervals. If a printer 

 is incorporated in the system, the recorder 

 simply presses a button and the lane count 

 at that instant is printed on a paper tape 

 and a fix mark is drawn on the fathogram. 

 The printed numbers are copied in the sound- 

 ing record and read off to the plotter who 

 records them on the plotting abstract, Form 

 817. Each position number is marked on the 

 printed tape record for easy identification. 



If a printer is not used with the Raydist, 

 two observers may be required to read the 

 phasemeter dials at the mark. When the 

 vessel is proceeding at full speed it is almost 

 impossible for one person to read both dials 

 correctly unless the sounding line is tangent 

 to one distance arc. 



The brush recorder automatically records 

 the changing lanes (Fig. 20). As a guard 

 against loss of the lane count, one man is 

 stationed at this recorder and makes fre- 

 quent comparison between it and the phase- 

 meter dials. The lane count is marked on 

 the graph at regular intervals, usually in 

 units of 5 or 10 lanes. Unless the graph is 

 needed to support lane count corrections, it 

 may be discarded at the end of the day. 



5-49 The operation of position fixing. — 



The detailed operations of position fixing 

 varies with the method of control being 

 used ; but the general procedure is the same 

 regardless of the method of control. All op- 

 erations are carefully related in time, and 

 certain operations must be performed by 

 various individuals at the same instant. The 

 recorder signals that the time for a fix is 

 approaching, gives a second warning a few 

 seconds before the fix, and signals the time 

 for the fix. If all members of the party are 

 in close contact, all of the above may be 

 done orally, otherwise an electric buzzer or 

 bell may be used to give the signals. 



(a) Sextant fix. — When sextant angles 

 are used to control the hydrography, the 

 operation of taking a fix is generally as fol- 

 lows. At the last sounding before the fix 

 the recorder calls, "On the next!" If the 

 interval between soundings is very short, or 

 if signals are faint, more time may be al- 

 lowed by calling, "One minute!" or "Two 



to go !" About 10 seconds before time for the 

 fix the recorder calls, "Stand by !" and at the 

 exact clock time for the fix he calls, "Mark !" 

 The anglemen should keep the angles cor- 

 rectly measured from the last warning until 

 the mark and should not change the angle 

 thereafter until the fix has been plotted. At 

 the mark, the echo sounder operator makes 

 a fix mark on the fathogram and reads the 

 sounding. The left angleman calls out his 

 angle first and then the right angleman calls 

 his angle. The plotter or left angleman gives 

 the names of the signals used in the fix. The 

 recorder must repeat all data as he records 

 them (see 5-54). 



(b) EPI or Shoran fix. — The procedure 

 for observing an EPI or a Shoran fix is 

 quite similar. A minimum of one minute is 

 usually required for observing an EPI fix, 

 but a Shoran fix can be observed in a few 

 seconds. The recorder issues a first warning 

 of "One minute to go!" or "On the next!" 

 The operator matches the pips in the scope 

 and keeps them matched from the call of 

 "Stand by!" until the mark. The distance 

 readings are called out for each station and 

 repeated by the recorder as he enters them 

 in the sounding record. The dials should 

 not be disturbed until the position has been 

 plotted. The echo sounder operator marks 

 the position on the fathogram and reads the 

 sounding. 



(c) Raydist fix. — Since Raydist shows the 

 position data continuously, the lengthy 

 stand-by period is not necessary. The re- 

 corder notifies the plotter that a fix will be 

 taken at the end of the next sounding inter- 

 val, pushes the marker button at the proper 

 time, transcribes the printed dial readings 

 to the sounding record at the same time 

 calling them out to the oflticer in charge. If 

 a printer is not used, a 10-second warning 

 is given and, at the mark, the person moni- 

 toring the brush recorder reads one dial, a 

 second man reads the other dial, and the 

 echo sounder operator marks the fathogram. 



5-50 Plotting positions. — Three-point 

 fixes are plotted with a three-armed pro- 

 tractor (see 3-16) or by use of circles of 

 equal angle (see 5-13). Plastic protractors 



