Multiple Reflection Techniques Used to Measure and Model a British Cannon Recovered from the Battle of Yorktown

Abstract

The utilization of a noncontact laser radar, multiplereflection measurement technique was employed to generate an accurate 3-D model of a historic artifact, both on exterior and interior surfaces. The artifact scanned was a “four-pounder” British naval cannon (as seen in figure 1) from the deck of a supply ship ordered scuttled in the York River by General Charles Cornwallis just prior to his surrender to General George Washington at Yorktown, Virginia, in the fall of 1781. Measurements were taken directly and with a single mirror on the entire exterior, while the interior bore was scanned using multiple mirror techniques. Difficulties encountered during the scanning process of the bore are described in this paper. Problems were both technical and environmental and included interior illumination, reference tooling ball acquisition, reflection angle and 4 The Journal of the CMSC/AUTUMN 2006 condensation. The data were aligned and processed with the final result being a watertight, polygonal model with an overall accuracy of 8100 µm (0.004 in.). This model has revealed interesting detail regarding eighteenth-century armament design and period casting techniques and will be used as the baseline to compare the restored artifact to its recovered condition.