6854 



HYDROGRAPHIC MANUAL 



Page 654 



and a velocity of sound of 1,490 meters per second, for the special case where the bomb- 

 ing station is directly over the ship's hydrophone. 



Table 22. — Ship's run corrections 

 [In seconds] 



Table 22 may be used as a basis for computing the corrections for any ship by adding 

 (or subtracting) the time interval equivalent to the distance between the bombing 

 station and the ship's hydrophone to those given in the table, provided this distance 

 is not too great, and provided further that the average surface velocity of the area does 

 not differ by more than 20 meters per second from that used to compute the table. 



The ship's run correction must not be used to correct time intervals obtained while 

 the ship is lying-to, bombing at buoys. A correction based on the average distance 

 from the buoy to the ship's hydrophone, the depth of detonation, and the velocity 

 of sound, must be computed and used to reduce the scaled times. 



(e) The elapsed time is the total time interval from the bomb explosion to the arrival 

 of the sound at the R.A.R. station. It is the scaled time plus the initial interval plus 

 the ship's run correction. 



The method of recording time intervals in the Bomb Record is described in 8311. 



6854. Disposition of Chronograph Tapes 



Immediately after the time intervals from a chronograph tape have been com- 

 municated to the plotting station, the values should be verified, if there is sufficient 

 time between positions, or if someone can be assigned to the chronograph station for 

 this purpose. The radio technician on watch may occasionally be able to do this 

 when he is not otherwise engaged. If the time intervals are not verified at this time, 

 this must be done later. The chronograph tapes must be marked for future identifica- 

 tion and folded and filed in a manner for easy reference. 



Chronograph tapes are marked for identification with rubber Stamp No. 41, 

 shown in figure 142, which provides spaces in which the position number, the day 

 letter, the sheet number, and the date should be entered. The stamp is used on the 



