This presentation is part of the International Cemetery Preservation Summit, October 8-10, 2014 Niagara Falls, NY.
Photogrammetric Documentation of Weathered and Damaged Headstones at the Cataraqui Cemetery,Kingston Ontario by George Bevan and Alexander Gabov
The Catarqui Cemetery in Kingston Ontario was incorporated on 10 August 1850 and contains the final resting place of Canada’s first Prime Minister, Sir John A. MacDonald, as well as over 46 000 individuals and families. In recognition of its significance both locally and nationally, the cemetery received the formal designation from the Canadian Federal Government in 2012 as a National Historic Site.
Unsurprisingly in a cemetery of this age there are many monuments that show damage from natural or human forces. From 2010 to 2011 Queen’s University and CSMO worked in a non-profit capacity to demonstrate that untrained student volunteers could deploy an imaging technique, first developed at HP Labs in 2001, Polynomial Texture Mapping (PTM), to reveal inscriptions that were difficult or impossible to read with the naked eye, as well as other salient features on the headstones, such as decorations and tool marks. Over 60 students were trained, and approximately forty stones documented.
Efforts from 2013-2013 focused on integrating GPS and stereo photogrammetry to create very accurate (<1mm) geo-located 3D models. Emphasis was placed on demonstrating that stereo-photogrammetry could provide data of equal or superior quality to PTM with only a single trained operator. Unlike PTM, which records the change in surface contour, photogrammetry uses pairs of overlapping images to generate dense clouds of 3D measurements. In cases of weathered stones where only the faintest depression remains from the original inscription, or where patination or lichen-grown has reduced contrast, grey-scale Depth Mapping can be used to bring out the original text. In this technique the deviations from an ideal plane corresponding to the surface of the stone are assigned grey-scale values, e.g. white represents deep incisions and black the surface.
George Bevan received his Ph.D. in Classics from the University of Toronto in 2005, and has taught in the Department of Classics at Queen’s University since 2007. George is also cross-appointed to the Department of Art Conservation, where he has investigated new imaging techniques of use to archaeologists and conservators, including X-ray Computed Tomography and Digital Photogrammetry.
Alexander Gabov is a Professionally Accredited Conservator and the owner of Conservation of Sculptures, Monuments and Objects (CSMO), a private firm specializing in the conservation of large-scale sculptures and monuments. Alexander is a former Adjunct Artifact Professor at the Queen’s University Art Conservation Program.