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Figure 84. — The plotting of 3- and 4-digit soundings at an angle is necessary to permit close 

 spacing of soundings required to portray irregular bottom configuration. 



the sounding interval and to avoid erroneous 

 spacing and positioning of soundings. 



6-60 Selection of soundings. — It is usu- 

 ally necessary to select soundings in the 

 record for plotting on the smooth sheet. It 

 cannot be emphasized too much that proper 

 selection of soundings is essential for com- 

 plete and accurate portrayal of bottom con- 

 figuration. The fathogram should be in view 

 when plotting soundings in order that the 

 plotter will have a proper conception of the 

 profile to be reflected by the soundings. If 

 it is evident that the recorded soundings re- 

 flect a mechanical or careless scanning of the 

 fathograms, it will be necessary to rescan 

 them. It is recognized that not all irregu- 

 larities can be represented at the scale of 

 the smooth sheet, and that minor relief in 

 very irregular bottom must be generally dis- 

 regarded. But it is essential that significant 

 peaks and deeps shall be scanned and plotted. 

 When selecting soundings which are inserted 

 at uneven intervals this action shall not re- 

 sult in small distorted numerals or numerals 

 which run together and fail to identify in- 

 dividual soundings. Under such conditions 

 the slope sounding should be omitted unless 

 it is advisable to select another sounding 

 from the fathogram. 



Inasmuch as the survey sheet should re- 



flect the relative density of hydrography, 

 the shoal and channel developments, investi- 

 gations, and crossline soundings should be 

 evident on initial inspection of the completed 

 sheet. In the event congested development 

 is partially plotted on an overlay (see 6-44), 

 a note on the sheet should highlight the 

 supplemental plotting. However, the least 

 depth and other depths needed for delinea- 

 tion of depth curves and bottom configuration 

 plotted on the overlay, shall be transferred 

 to the smooth sheet. 



Where routine plotting of soundings in- 

 volves overlaps or crossings of hydrography, 

 the shoaler soundings shall be plotted but 

 consideration shall be given to selection of 

 soundings and retention of the identity of 

 the sounding line. There should be no hesita- 

 tion about erasing previously plotted sound- 

 ings, but the deletion should not impair the 

 paper surface or legibility of adjacent 

 soundings. 



6-^1 Discrepancies in hydrography. — 



During the plotting of the soundings and 

 the delineation of the depth curves, the 

 smooth-sheet plotter must be ever alert 

 to detect errors in the hydrographic data. 

 Discrepancies related to control and hydro- 

 graphic positioning are discussed in 6-50, 

 but there is a great variety of errors which 



