Preservation and Archiving of Historic Murals using Digital Non-Metric Camera

Digital non-metric cameras with high-resolution capabilities are being used for various domains such as digital heritage, artefact documentation, art conservation and engineering applications. In this study the novel approach is in the application of the combined use of close-range photogrammetry (CRP) and mapping techniques, to capture the depth of the mural digitally serving as a database for preservation and archiving of historic murals. The open hall next to the main sanctuary of the Virupaksha temple in Hampi, Karnataka, India, which is also a UNESCO World Heritage site, depicts cultural events on a mural-covered ceiling. A mirrorless Sony Alpha 7 III camera with a full frame 24MP CMOS sensor mounted with a 50mm and 24mm lens has been used to acquire digital photographs with an image size of 6000 × 6000 pixels. The suggested framework incorporates five main steps: data acquisition, colour correction, image mosaicking, orthorectification, and image filtering. Results show a high level of accuracy and precision attained during the image capture and processing steps. A comparative study was performed in which for a 24 mm lens orthoimage resulted in an image size of 9,131 x 14,910 and pixel size of 1.05mm whereas for a 50mm lens it produced 14,283 x 21,676 image size and a pixel size of 0.596 mm of the mural on the ceiling. This degree of high spatial resolution is essential for maintaining the digital documentation having fine details of the artwork as well as its historical context, subtleties, and painting techniques. The study's findings demonstrate the effectiveness of digital sensors with the close-range photogrammetry (CRP) technique as a useful method for recording and preserving historical ceiling murals.