Laser Scanning Supporting Graving Dock Retrofit

In July 2004, Electric Boat Corporation decided to retrofit Graving Dock 3 at its Groton, Connecticut shipyard with a reinforced concrete wall designed and constructed to replace the existing cellular cofferdams that comprise the dock. Since the cofferdams are of various heights and have deflected in different ways over the years, an efficient method was needed to capture the as-built configuration of the graving dock before design of the wall could be finalized. The owner, design agent and contractor chose a combination of 3D laser scanning, post processing, and CAD modeling to capture this as-built condition. The resulting three dimensional CAD surface model of the dock became integral with the design of the wall and its construction. This paper will provide an overview of the reasons laser scanning was chosen and a description of how the laser scans were taken and processed. The paper will also discuss how a CAD model was created from the processed data, and more significantly, how the model was used in the development of design and construction drawings. The paper will conclude with a look at how 3D laser scanning is being used on other projects at Electric Boat, for both shipbuilding and facilities.