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HYDROGRAPHY 



Table 6. — Spacing of sounding lines 



3151 



Scale 



10,000. 

 20,000. 

 40,000. 

 80,000. 

 120,000 



Ordinary spacing 

 (4 to 5 lines to the inch) 



Meters 



50 to 60 



100 to 125 



200 to 250 . 



400 to 500 



600 to 750 



Closest spacing 



(8 to 10 lines to 



the inch) 



Meters 

 25 to 30. 

 50 to 60. 

 100 to 125. 

 200 to 250. 

 300 to 375. 



3151. Maximum Spacing for Various Coastal Areas 



Because of tlie widely different conditions encountered in different areas, it is 

 manifestly impossible to prescribe precise rules for the spacing of lines which will apply 

 in all cases, but a general understanding of the requirements may be gained from 

 examining figure 55 and from the discussions herein. It must be emphasized that the 

 graphs are not intended as requirements but represent the maximum spacing to be 

 tolerated in any given area at any given depth. It will frequently be necessary to 

 decrease this maximum spacing considerably even within the regions specifically 

 mentioned as typical for each graph. 



Figure 55. — Maximum sounding-line spacing. (See text.) 

 AA Flat sand or mud bottom without rocks, banks, or shoals. 

 BB Sand bottom with banks, but without rocks. 

 CC Areas with occasional rocky formations. 

 DD Areas with frequent steep rocky shoals and dangers. 

 EE Searches for shoals or dangers in oceanic areas. 



