8144 HYDROGRAPHIC MANUAL PaGE 764 



8144. Bottom Characteristics 



The character of the bottom shall be entered in the column headed "Bottom", with 

 the frequency specified in 3842, using the standard abbreviations from part "S" of the 

 Symbols and Abbreviations chart (fig. 189, part XI). Characteristics not on this 

 chart shall be written out in full. The proper interpretation of many of the terms and 

 miscellaneous instructions for recording them are given in 3845, 3846, and 3847. 



Detached determinations of the character of the bottom, as from the flukes of the 

 anchor, from a buoy anchor, or at a serial temperature station, must always be accom- 

 panied by a position — by the best estimated position from dead reckoning if a fixed 

 position cannot be obtained (see 3841). 



8145. Compass Heading 



The vessel's heading by compass at all times during sounding shall be entered in 

 the column headed "Heading by Compass" ; and in the blank 



space shall be indicated whether the steering or standard magnetic compass or gyro- 

 compass of major survey units is in use. 



In launch and small-boat hydrography controlled by three-point fixes, and in hydro- 

 graphy controlled by ranges or distance angles, compass headings may be omitted. If 

 they are omitted, the general direction of the line being run (unless distance angles are 

 used) shall be entered in the "Remarks" column. If ranges or distance angles are 

 being used that fact shall be entered vertically in the compass heading column. With 

 the above exception, no entries except headings shall be made in this column. Entries, 

 such as c/c and o/c to indicate "changed course" and "on course" properly belong in 

 the "Remarks" column. 



All courses shall be entered in degrees, clockwise from north. 



Course entries in connection with changes in course and turns shall be in accordance 

 with 3454 and 3463. A time entry should be made in the "Time" column opposite each 

 course entry. 



8146. Position Data 



Insofar as practicable, all position data, except R.A.R. distances, shall be entered 

 in the column provided in the center of the right-hand page. It is disconcerting to have 

 a part of these data recorded in the "Remarks" column. 



The first entry of position data shall invariably be on the same horizontal line with 

 the corresponding time and position number on the left-hand page, followed on conse- 

 cutive lines by the remainder of the position data. The position number and symbol 

 which appear on the left-hand page shall be repeated immediately to the left of the top 

 entry of position data (see 8141). 



The required frequency of position is specified in 3313 and 6812. 



Three-point fix. — The names of the three stations of a three-point fix shall be re- 

 corded vertically in the left part of the column, with the name of the center station 

 indented slightly. The objects shall always be recorded clockwise, that is, the left 

 object first, the center object next, and the right object last. The angles are recorded 

 in the right part of the column, the left and right angles being recorded opposite the 

 names of the left and right stations respectively. 



A three-point fix shall always be recorded between two heavy ruled horizontal 

 lines, leaving as many blank spaces in the "Time" and "Soundings" columns as are 

 necessary to accomplish this. 



