Figure 2. Side scan sonar in operation 



22. Essentially, the slant-range correction assumes a flat seabed with 

 low target relief. Thus, any violation of this assiomption introduces some 

 distortion in the plotted horizontal position (range) of targets, notably 

 sloping or undulating bottom and projecting targets. An example pertinent to 

 coastal applications is a sloped breakwater face on a flat bottom. The break- 

 water face will be plotted steeper than it really is, image -corrected or not. 



23. An optional digital data recorder may be useful to redisplay the 

 image at the office, for duplicate copies or for experimenting with different 

 enhancement or correction techniques . 



24. The key aspects of a desirable survey boat relate to providing a 

 protected, convenient, and electro -mechanical noise-free environment for the 

 control unit and to positioning the towfish so that image quality and useful- 

 ness are maximized. The vessel must follow a prescribed course at relatively 

 low speed while transmitting a minimum of yaw, pitch, and roll motions to the 

 towfish. These objectives can be difficult to achieve in shallow-water condi- 

 tions, unlike in deep water where the long length of the tow cable helps damp 

 out transmitted motions. Erratic motion of the towfish will decrease the 



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