INTRODUCTION 



The objectives of this study were to determine and summarize the 

 requirements and the methods for selecting and surveying an ocean site for 

 on-bottom installations. In accordance with the objectives, the various para- 

 meters significant to designing, constructing, operating, and maintaining a 

 bottom installation were established. Simultaneously, a study to determine 

 the state-of-the-art methods and equipment to assess the values of these 

 parameters in site survey operations was conducted. 



The purpose of this report is to present the findings from this study 

 and also to supplement earlier reports 1 - 2,3 by the Naval Civil Engineering 

 Laboratory (NCEL) in the area of ocean construction and site surveys. This 

 report discusses parameters significant to engineering site surveys and the 

 procedures and state-of-the-art techniques available to assess the values of 

 these parameters. 



Since this report is written with the assumption that the reader has 

 an understanding of the concepts of site surveying, specific step-by-step 

 descriptions will not be included. The more significant aspects of site sur- 

 veying for ocean floor structures will be covered. 



Site surveying capabilities for engineering applications in the ocean 

 are currently deficient. Site surveys conducted for general oceanographic 

 and geological studies do not demand the precision required in civil engineer- 

 ing. Positioning in the ocean is one deficient area, and the remoteness of the 

 bottom relative to a surface vessel compounds this problem. As a consequence, 

 horizontal control is inadequate to survey areas of 500 feet by 500 feet with 

 sufficient precision that a structure can later be founded on a relatively level 

 area 50 feet by 50 feet within the surveyed area. 



The problem of site surveying for engineering applications will be 

 partially solved by the development of precise positioning techniques. The 

 other aspect of the problem is the measurement techniques required to assess 

 the values of the site survey parameters. Possibly an absolute system of on- 

 bottom horizontal control from which data points can be referred will 

 ultimately be required for positioning. (An absolute system refers to one 

 which is integrated with the absolute coordinates of the earth.) As an 

 intermediate goal, it is desired to have horizontal controls accurate to 



