Page 771 records and reports 822 



In depths over 100 fathoms, all corrections may be omitted where the algebraic 

 sum of the maximum tide correction for the day's work and all other corrections is 

 less than one-half percent of the depth. Thus in reducing echo soundings, if the velocity 

 correction for 350 fathoms is — 0.7 fathom and the maximum tide reducer for the day 

 is —0.7 fathom, the corrections may be omitted for that depth because the sum 

 of the corrections is only 0.4 percent of the depth. On the contrary, if the maximum 

 tide reducer were —1.1 fathoms, the total correction would be slightly greater than 0.5 

 percent of the depth and corrections could not be omitted, even though at the actual 

 time of sounding the tide reducer may have been such as to bring the total correction 

 below 0.5 percent. Corrections must not be or ittod when the tide is low and entered 

 when it is high. 



Corrections shall be entered according to table 29 (see 8143). It should be noted that, in general, 

 the corrections are to be entered to a decimal which is one-half that required in recording the sound- 

 ings, using 0.2 where the requirement for recording is 0.5. Exceptions are: that no entry in feet 

 need be closer than 0.2 foot and no entry in fathoms need be closer than 0.1 fathom; and for sound- 

 ings over 60 feet, except on shoals and banks, corrections need be entered only to the nearest foot. 

 Used in conjunction with table 29, the following tabulation may be helpful: 



The range through which any correction is to be applied is as follows: 



Where corrections are entered to the nearest 0.5 foot or less, and to the nearest 0.1 fathom, the 

 range covered shall be from one-half below to one-half above the correction applied, according to the 

 following tabulation: 



Whether added to or subtracted from the sounding 



Range 



0. 1 to 0. 3 foot = 0. 2 foot 

 0. 3 to 0. 5 foot = 0. 4 foot 

 0. 5 to 0. 7foot = 0. 6 foot 

 etc. 



0. 25 to 0. 75 foot = 0. 5 foot 



0. 75 to 1. 25 feet= 1. foot 



1. 25 to 1. 75 feet=l. 5 feet 

 etc. 



0. 05 to 0. 15 fathom ==0. 1 fathom 

 0. 15 to 0. 25 fathom = 0. 2 fathom 

 0. 25 to 0. 35 fathom = 0. 3 fathom 

 etc. 



