CHAPTER 5 

 NAVIGATION AND SONIC SOUNDINGS 



5-1 GENERAL REMARKS— Obtaining 

 detailed and accurate sounding data for im- 

 mediate and future use is of prime importance 

 to the fleet and merchant marine. Navy survey 

 ships are required to take continuous soundings 

 while underway and frequently take intensive 

 soundings over selected areas. Careful atten- 

 tion to navigation, plotting corrected ship's 

 tracks, recording soundings, and correctly mark- 

 ing the echogram is of utmost importance. 



It is not within the scope of this manual to 

 attempt to cover the various aspects of hydro- 

 graphic surveys. However, in view of the im- 

 portance of accurate navigation and sounding 

 information to oceanographic observations, the 

 following general instructions are given. These 

 instructions apply to Navy ships conducting 

 oceanographic surveys. They may be added to 

 or modified by specifications for a particular 

 cruise when circumstances so demand. 



5-2 NAVIGATION.— Navigation of the ship 

 is not expected to present any more than the 

 usual problems. The value of the data collected 

 will be much greater if the ship's position is 

 determined so accurately as to leave no ques- 

 tions for the future. 



Whenever two or more ships are conducting a 

 survey and proceeding in company, it is desired 

 that they maintain a range between ships of 

 at least five miles. This will give a better spread 

 of soundings and prevent overlapping track 

 lines on the final compilation sheets. 



5-3 Plotting Sheets. — For each survey 

 cruise, two sets of contoured position plotting 

 sheets (H. O. Series 3000) will be furnished the 

 ship. These sheets cover all areas of the survey 

 and are numbered and coded by the Hydro- 

 graphic Office. On one set are plotted the posi- 

 tions of the proposed oceanographic stations, 

 any special sounding grids, and the recommend- 

 ed ship's track for the cruise. This set is the 

 navigator's worksheets, or rough plots. The 

 other set is used for plotting the corrected ship's 

 track, soundings, stations, and other observa- 

 tions. It is the smooth track plot. 



5-4 Information to be Furnished by the 

 Navigator. — The following information is to be 

 furnished by the navigator: All fixes, celestial, 

 Loran, sun lines, geographic bearings; a DRT 

 position for each fix for the purpose of com- 

 puting set and drift; and all changes of course 

 and speed, with times noted. Local zone time 

 shall be used and time zone changes noted. 

 At each fix, especially the morning, local appar- 

 ent noon, and evening fixes, the navigator shall 

 give his evaluation of the fix with comments 

 about weather conditions; i. e., poor horizon, 

 good horizon, hazy, clear, cloudy, etc. Time of 

 arrival at and departure from stations shall be 

 given, with proper allowances for maneuvering 

 the ship. 



The navigator shall indicate the corrected, or 

 actual, ship's track between the best available 

 fixes. This track shall be shown in blue pencil 

 and shall be used to construct the smooth plot 

 track. Any notes or changes made on the 

 navigator's worksheet by any person other than 

 the navigator or his assigned personnel shall be 

 made with colored pencil (other than blue). 

 A sample sheet is shown in figure 5-1. 



5-5 Preparation of the Smooth Track 

 Plots. — The smooth track plots shall be con- 

 structed from the corrected ship's track, in- 

 dicated in blue on the navigator's worksheet. 

 Times plotted on the smooth sheets shall be 

 underlined so as not to be confused with sound- 

 ings. Local zone times shall be noted every 

 hour, for every change of course and speed, and 

 for time of arrival at and departure from sta- 

 tions. The soundings shall be plotted at 10- 

 minute intervals, except that where more detail 

 is needed the interval shall be closer. All 

 soundings shall be taken from the echograms 

 and shall be checked against those recorded in 

 the sounding logbooks. The bathythermo- 

 graph slide number shall be plotted for each 

 observation made. A sample sheet is shown in 

 figure 5-2. 



5-6 SONIC SOUNDER INSTRUCTIONS.— 

 The sonic sounders shall be operated continu- 



H. O. 607 



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