13 Pattern Matching and the Analysis of Damaged Ancient Objects: The Case of the Column Drum PHILIP SAPIRSTEIN and ERIC PSOTA, University of Nebraska–Lincoln We describe a common problem in the curation and analysis of archaeological materials: restoring the orientation and dimen- sions of damaged objects. Our focus is a common architectural type in Mediterranean sites, the Doric column drum, which we investigate at one of the earliest Doric temples in the Greek world, the Hera temple at Olympia. The 3D modeling and analysis of this building by the Digital Architecture Project since 2013 has revealed new insights into the construction history of its stone colonnades. This paper concerns the analysis of the 3D models of the in situ material, using the almost 100 fallen drums and capitals to reconstruct the colonnade digitally. In order to accomplish this, we propose two novel methods for training the machine to estimate the dimensions of a fragmentary column drum. One approach is a modification of ICP, where the fragment is compared to an ideal model of an intact drum, which is resized iteratively until concluding with a satisfactory fit. Another approach recasts the scan data into polar coordinates and uses RANSAC to identify the exterior profiles of the piece and remove points likely to belong to damaged areas. The filtered points are then examined by the algorithm to estimate the radii and taper of the drum. Besides saving a great deal of time in the field, these methods are also accurate to within 0.2% of the total radius for well-preserved material, and 1% for even the most fragmentary drums at Olympia. These data have allowed the digital reconstruction of 80% of the displaced drums and all of the capitals from the temple. Our algorithms can be used to measure any fluted column drums, and we discuss the potential value of our approach for other categories of archaeological artifacts. CCS Concepts:  Computing methodologies → Point-based models; Reconstruction;  Applied computing → Architecture (buildings) Additional Key Words and Phrases: Greek architecture, digital reconstruction, algorithmic measurement, damaged artifacts ACM Reference Format: Philip Sapirstein and Eric Psota. 2016. Pattern matching and the analysis of damaged ancient objects: The case of the column drum. ACM J. Comput. Cult. Herit. 9, 3, Article 13 (September 2016), 22 pages. DOI: http://dx.doi.org/10.1145/2901297 1. INTRODUCTION Archaeologists spend much of their time examining fragments of damaged objects. Once the material is sorted and classified, they hope to discern patterns and to develop a synthetic narrative reconstructing The Digital Architecture Project is funded by the University of Nebraska–Lincoln, including the Department of Art & Art History, the Hixson-Lied College of Fine and Performing Arts, and the Center for Digital Research in the Humanities. Authors’ addresses: P. Sapirstein, School of Art, Art History & Design, UNL, 120 Richards Hall, P.O. Box 880114, Lincoln NE 68588-0114; email: psapirstein2@unl.edu; E. Psota, Department of Electrical & Computer Engineering, UNL, 209N Scott Engineering Center, P.O. Box 880511, Lincoln, NE 68588-0511; email: epsota@unl.edu. Permission to make digital or hard copies of part or all of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies show this notice on the first page or initial screen of a display along with the full citation. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, to republish, to post on servers, to redistribute to lists, or to use any component of this work in other works requires prior specific permission and/or a fee. Permissions may be requested from Publications Dept., ACM, Inc., 2 Penn Plaza, Suite 701, New York, NY 10121-0701 USA, fax +1 (212) 869-0481, or permissions@acm.org. c  2016 ACM 1556-4673/2016/09-ART13 $15.00 DOI: http://dx.doi.org/10.1145/2901297 ACM Journal on Computing and Cultural Heritage, Vol. 9, No. 3, Article 13, Publication date: September 2016.