Page 209 hydrography 3244 



should be examined critically to determine whether the area is being adequately covered, 

 and where additional splits or development should be added; or whether the adopted 

 spacing is unnecessarily close. If splits and additional development are not occasionally 

 necessary the regular system of lines is almost certainly uneconomic. 



3244. Revision of Topography 



On an inshore hydrographic survey the boat sheet is used for indicating any changes 

 or errors in the high-water line and in the offshore details transferred from the topo- 

 graphic sheets. Such corrections shall be shown in red with appropriate notes added 

 explaining the method of location used. (See 3811.) 



Sextant cuts to locate a rock, breaker, hydrographic signal, or other feature should 

 be carefully plotted on the boat sheet, the penciled lines being left to indicate the posi- 

 tions from which the cuts were taken. All pertinent data should, in addition, be 

 recorded in the Sounding Record so that they may be plotted independently on the 

 smooth sheet. 



Isolated rocks or groups of rocks not yet accurately located should be noted on 

 the boat sheet in their approximate positions, with notes to indicate the probable 

 accuracy of position in case it is not practicable for any reason to locate them subse- 

 quently by a more accurate method. Where it is not practicable to locate the limits 

 of reefs, breakers, kelp, etc., by three-point fixes, they should be sketched as accurately 

 as possible and adequate descriptive notes should be added to guide the smooth-sheet 

 plotter in case any such features have to be transferred from the boat sheet to the 

 smooth sheet. 



The height of each isolated rock, or the highest of a group, shall be entered in the 

 Sounding Record, together with the date and time of observation, so that the correct 

 tide reducers may be subsequently entered to obtain the elevation of the rock with 

 reference to the appropriate datum plane. The approximate height should be noted 

 on the boat sheet. (See 7821.) 



3245. Station Names 



All control stations used in the survey must be named on the boat sheet, and the 

 spelling and usage of station names recorded in the Sounding Records must agree with 

 the boat sheet. (See also 215 and 3231.) 



The symbols and names of stations appearing on the boat sheet but not used during 

 the survey shall be crossed out in ink to indicate that they are not needed on the smooth 

 sheet. 



3246. Daily Inspection of Boat Sheet 



The boat sheet should be reviewed daily by the hydrographer. At this time he 

 should plot all positions which could not be plotted during the day, and rectify the data 

 in the Sounding Record to correspond. Corrections should be made to erroneously 

 recorded data, omissions should be supplied while the details are fresh in mind, and 

 notes should be made that are required to explain fully any data which are not self- 

 evident. (See 81 and 818.) This examination will also disclose the adequacy of the 

 recorded data and shortcomings can be brought to the attention of the recorder. 



By this daily examination, the hydrographer determines whether the area is 

 being adequately covered and developed, whether there is agreement in depth between 

 soundings on adjacent lines and at crossings of lines, whether there should be additional 

 sounding on shoals and dangers, whether all previously charted shoals and dangers 



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