perpendicular to the line of travel is a function of the height of the fish 

 and the distance of the object from the fish and oscillations in these posi- 

 tions. Microprocessor-controlled image processors can be used to print true 

 one-to-one scale sonographs, making both the slant range correction mentioned 

 above and changing the scale of the along track direction to match the slant 

 range scale. 



Other aids for inter- 



preting side-scan sonar images 



17. Ease of interpreting side-scan sonar image records can be signif- 

 icantly improved by several factors not related to the equipment or physics. 

 First, interpreting side-scan sonar images of structures is much easier if 

 they can be compared to construction drawings, preferably as-builts. The 

 drawings can be used to plan the survey as well as significantly aid interpre- 

 tation. Second, supplementing the side-scan sonar inspection with limited 

 diver observations can aid in deciphering a questionable feature on the sono- 

 graph. Finally, a knowledgeable engineer familiar with the history of a 

 structure can facilitate interpreting the sonograph. 



14 



