Research and Development of a Photogrammetric Condition Monitoring Workflow to Improve Change Detection in Wall Paintings

In the field of wall painting conservation, condition monitoring plays a key role in assessing the stability of a painting by determining if detrimental change is occurring over time. Condition monitoring typically involves a visual comparison between the painting and a previously captured photograph or image and relies on the ability of a conservator to observe visible change. In practice, the monitoring of wall paintings can be challenging given the potential range of condition phenomena, complexity of material composition, uneven surface topography and issues of scale, access, and lighting. Using two-dimensional images alone to detect change, across large surface areas and in depth, is often insufficient and can result in misleading or incomplete assessments of condition. To improve the detection of change in wall paintings, the Getty Conservation Institute initiated research between conservators and heritage recording specialists to update and validate a photogrammetric condition monitoring workflow that can identify three-dimensional change using readily available and cost-effective equipment. This paper describes the workflow and the experimental trials conducted to characterize its precision and accuracy. The results of this initial research demonstrate that an affordable, photogrammetric workflow can reliably detect and quantify sub-millimeter change in wall paintings, improving current condition monitoring practice.