V. CONCLUSIONS 



As a result of this study we have reached the following conclusions: 



1. The accuracy requirements for acoustic velocity data may be 

 either relative or absolute. Relative accuracy in the shape of the 

 velocity profiles is usually sufficient for tactical needs. However, for 

 long range surveillance in the deep sound channel, high absolute accuracy 

 may be required. 



2. Velocimeters are well suited to surveying the deep sound channel. 

 The use of velocimeters can reduce the error in location of a distant object 

 by a factor of at least 2 to 4 times the possible error which would occur 



if X.B.T.'s were employed. The principle error in the use of an X.B.T. 

 at great depth is in the pressure correction term because of the error 

 in depth location. The projected range error due to computed velocity 

 at the sound channel axis using an X.B.T. based on a temperature error 



of + 0.2°F and 2 to 3% projected depth error at about 1500 meters depth 



(1) 

 is between 0.04 and 0.06%. 



3. The present velocimeters are adequate for survey purposes. 

 The manufacturers are aware of the problems and attempt solutions. 

 However, there has been in fact little development beyond the original 

 sing-around system, presumably since the returns from limited sales of 

 velocimeters do not warrant extensive development programs. 



(1) 



Comprehensive tests performed in May 1968 aboard the NRL research 

 vessel Mizar have shown that the standard deviation of the fall rates 

 of 6,000 ft. deep X.B.T.'s is less than 1%. If any bias on this data is 

 shown to be less than 1% then the absolute values of the fall rate at 

 various depths will be known to an accuracy of 1%. Thus this precision 

 between X.B.T.'s would allow prediction of B.T. depth to 1%. A report 

 detailing these tests is now in preparation for NAVSHIPS, Code 00V1H. 



51 



arthur ZD.lUttle.Knr. 



