Page 553 echo sounding 582 



The operation otherwise is similar to that used in distance finding in R.A.K.. The 

 bomb explosion is received through the ship's hydrophone and recorded on the chrono- 

 graph, the echo received later from the bottom being also recorded. The time intervals 

 are scaled as in R.A.R. (6853), and the same "ship's run corrections" are added to the 

 scaled values. A constant equal to the mean depth of the bomb explosion and the 

 ship's acoustic receiving unit must be added to the final result. 



Comparisons indicate that depths measured in this manner in about 2,000 fathoms 

 are, on the average, less by some 15 fathoms than simultaneous depths measured by 

 echo-sounding instruments. The data are inconclusive but seem to indicate that 

 sounding with bombs should give results within the specified accuracy of 99.5 percent 

 for depths of 3,000 fathoms or greater. 



Sounding with bombs is authorized only for experimental purposes or in an emer- 

 gency in deep water, when authorized methods fail to give results. 



