Comparison of carved panels from two Irish high crosses using laser scans

We present the results we obtained in comparing several carved panels from two high crosses. In this study, which was carried out as part of the RTE Cork TV program "Secrets of the Stones", we compared three panels of the Cross of the Scriptures from the Clonmacnois monastic site, Co. Offaly with similar panels from the Cross of Durrow, located in the grounds of St Columba monastery, Co. Offaly. The purpose of the study was to decide whether these high crosses, which both date back to the ninth century, could have been carved by the same Celtic artist. The Cross of the Scriptures was scanned in August 2008 using our Polhemus FastSCAN handheld laser scanner, while the Cross of Durrow was surveyed in May 2008 by the Germany based, ArcTron 3D company, commissioned by the Offaly County Council. Using the data from the 3D scans, details of each panel were enhanced using a wavelet filtering technique and a false colour image of the depth field was computed for each panel. These images were then used as textures and applied back onto the 3D models. This process allowed for expert historians to later on evaluate, by looking and manipulating the textured 3D models, the hypothesis that the panels were carved by the same person.