Three-Dimensional Modelling and Visualization of Stone Inscriptions Using Close-Range Photogrammetry—A Case Study of Hero Stone

Abstract

Stone inscriptions and archaeological structures are an asset to humankind which contain the history of the past. Estampage is the traditional method used to obtain the replica of the inscriptions which is primarily used to decrypt texts and for documentation purposes. Presently, close-range photogrammetry is a useful remote sensing technique to digitize these inscriptions for study as well as preservation. The current study focuses on the creation of a 3D model of a hero stone using digital camera technology. These photographs were acquired using a Sony Alpha7 III camera with a 35 mm full-frame CMOS sensor. Two hundred and sixty-one images/frames were acquired from different heights above ground and with various positions and angles around the stone inscription to cover it all around. The data acquired were processed in a series of steps which included image matching, dense point cloud generation, mesh reconstruction, and texturing of the model. As the sensor is non-metric, two markers acquired from the field were added to the scene to scale it accurately. The dimensions of the hero stone are computed as 2.3 × 1.3 ft and the resulting model had a reprojection error of less than 0.011 pixels. The processed model has 10,915,514 facets (TIN) and 8000 × 8000 × 4 textures providing a realistic appearance. The recent developments in computer vision using the structure from motion (SfM) approach enables the reconstruction of the hero stone accurately with realistic textures and details useful for preservation work.

Keywords

• close-range photogrammetry
• inscriptions
• digital documentation
• structure from motion
• heritage preservation