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HYDROGRAPHIC MANUAL 



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are required in units of tenths of fathoms, the change points should be taken at 0.05 

 fathom points, and these change points should be marked on the curve; thus, for 

 example, if the correction +0.5 fathom is found to be on the correction curve at a 

 depth of 75 fathoms, the correction +0.6 fathom at a depth of 85 fathoms, and the 



(t^t 1 inch CQUill 4 lolhomi tor deep water and 1 inch equal -i tatbom tor ihoal.) 



Figure 114. — Curve of velocity corrections to echo soundings. 



correction +0.7 fathom at a depth of 95 fathoms, the tabulation should show that the 

 correction +0.6 fathom is applicable for all depths from 80 to 90 fathoms. 



These velocity correction curves should be included in the velocity of sound report 

 (see 8332), but a tabulation of the velocity of sound corrections shall be included in the 

 Descriptive Report for each hydrographic survey (see 8434). 



