the records. Finally, there is no substitute for visual confirmation of a 

 questionable image. Unexplained features, especially those suggesting an 

 inconsistency in the structure, should be checked by divers or a Remotely 

 Operated Vehicle (ROV) if possible. A few direct observations can be used to 

 help understand a number of miles of records by providing information on key 

 questionable features on the side-scan sonar records. Good position control 

 during the side-scan sonar survey is required to allow the diver or ROV 

 operator to return to the location of the questionable image. 



Structure Type 



79. The type of structure to be surveyed will also influence the qual- 

 ity of the record and success of the survey. Structure slope, cover unit 

 size, pattern of placement, and relief of the units will all affect the detail 

 which can be interpreted from the record. Steep-sloped zones on the structure 

 face can shadow other portions of the structure. Slope changes and berms 

 should be easy to identify. The larger size and more regularly shaped armor 

 stones (e.g. rectangular blocks) and armor units (e.g. dolosse) are readily 

 identifiable in most cases. Regular patterned placement plans (e.g. laid-up 

 blocks) give a less confused image than randomly placed units (e.g. typical 

 rubble-mound construction). An armor cover made up of high relief small units 

 will result in a patterned image which is more abstract. 



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