Rules of Thvunb 



27. Details and rules of thumb for consideration to aid in SSS opera- 

 tion include : 



a. Environmental limitations: 



(1) Wave heights less than 5 ft at shallow-water (under 100-ft 

 depth) sites; in depths less than 20 ft, near calm 

 required. 



(2) Survey during high water slack for maximum depth, minimum 

 currents . 



b. Deployment method: 



(1) Tow point on center line at bow, with 10- to 20-ft boom 

 extension. 



(2) Midships tow point preferable in special circumstances. 



c. Tow speed is a minimum of 1 knot, typically 2 to 4 knots. 



d. Towfish depth: 



(1) One-half to two-thirds of average depth at shallow-water 

 sites (single pass) . 



(2) 10 percent of range setting in deep water, noncorrecting 

 SSS system. 



(3) 15 to 40 percent of range in deep water, auto-correcting 

 SSS system. 



e. Frequency: 



(1) 100 kHz for reconnaissance, screening, or rough-water 

 survey . 



(2) 500 kHz for close range, detailed inspection. 



f. Range: 



(1) 25 m or greater, depending on safe operating distance 

 (100 kHz). 



(2) 50 m, 75 m, detailed inspection (500 kHz). 



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