96 



HYDROGRAPHIC MANUAL 



Table 31. — Rubber stamps for survey records 



Page 872 



96. TABLES 



In this section is included a variety of tables, diagrams, and lists, which the hydrog- 

 rapher may need to use repeatedly without reference to the text. Most of them have 

 been prepared especially for convenient use in hydrographic surveying, and others 

 are not readily available elsewhere. 



961. Velocity of Sound Tables 



The velocity of sound in sea water is of supreme importance in hydrographic sur- 

 veying, since most of the depths are now measured by echo sounding and much of 

 the control of offshore hydrography is by Radio Acoustic Rangmg (R.A.R.). It is 

 necessary to use the velocity of sound in sea water in connection with both echo 

 sounding (see 561) and R.i^.R. (see 636). Two methods of deriving the velocity of 

 sound from the observed physical characteristics of the water are provided: (a) from 

 tables, and (b) from diagrams. Velocities derived from the tables will be slightly 

 more accurate than those scaled from the diagrams, although the latter should be 

 sufficiently accurate for all uses in hydrogi'aphic surveying. 



9611. Velocity of Sound Computations 



If the temperature and salinity of sea water at a specific depth are known, the 

 velocity of sound at that depth may be derived from tables 32, 33, and 34, 

 These tables are based on Tables of the Velocity of Soimd in Pure Water and Sea 

 Water, H. D. 282, published by the Hydrographic Department of the British Admiralty. 



