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3D Heritage Recording of Archaeological Site Features

1996 - Israel

In 1996, in collaboration with the Israel Antiquities Authority and Robin Letellier, a consultant in heritage recording, NRC undertook a pilot project to demonstrate the 3D heritage recording applications for archaeological site features for conservation professionals in Israel. A Large Field of View scanning system was used to scan the Arcosolia Room Tomb of St. James in Jerusalem as well as several archaeological and architectural site features at Caesarea. Each site was used to demonstrate a different heritage recording application.

The Arcosolia Room of St. James Tomb

The Arcosolia Room measures approximately 2 m x 2 m x 1.8 m in height. It has been carved in the rock and the interior surfaces are rough and irregular in shape. Architectural and archaeological sites, which have surfaces of this nature, are difficult to accurately record with a high level of detail using conventional recording techniques such as traditional survey methods, rectified photography, stereo-photogrammetry, distance meters, etc. The objective was to digitize the entire interior of the Tomb to prepare an archival record for conservation documentation (Figure 1). In addition, the data was used to prepare an interactive 3-D VR theater display of the Tomb in actual size to demonstrate the application for "virtual tours" of the site.

The entire interior of the Tomb was recorded with a lateral resolution of 2 mm in X and Y and a depth resolution (Z) of 0.3 mm in one half day of on-site recording time using a portable generator. Subsequently, approximately 4 to 5 days were required off-site to prepare the 3-D digital model.

Figure 1a: Entrance to St James Tomb in Jerusalem. The Tomb measures approximately 2 m x 2 m x 1.8 m in height.

Figure 1b: The Large Field of View camera scanning the entrance.

Figure 1c: Cut away views on the 3D digital model.

Figure 1d: Views of the Tomb entire shape as a cloud of points as it would appear from an artificial point of view embedded in the rock.

Figure 1e: Orthographic projections of the four walls where perspective effects are removed to preserve proportions. In addition to recording the irregular shape details with accuracy for heritage preservation documentation, the digital model data can also be used to prepare 3D Virtualized Reality displays for VR theatre applications. The rough and irregular surface details of archaeological sites captured by the system add considerable realism and authenticity to VR displays which are often lacking in flat synthetically modeled displays.

3D Recording of Mosaic Flooring at Caesarea

The archaeological site at Caesarea on the Mediterranean coast contains Roman and mosaic flooring. With small and irregular spaced tiles and patterns, mosaic flooring is often difficult and time-consuming to accurately record using conventional archaeological recording techniques. One of the conventional recording techniques used to record floor mosaics is rectified photography. When printed to scale, rectified images can be traced over to produce a line drawing of the floor details.

3D scans of a floor mosaic can be used to achieve the same results with greater accuracy and with the added value that the information provides a 3D metric representation of the floor surface. This accurate 3D representation provides condition data that is not easily visible in 2D. Algorithms can be written to allow extraction of edges of well-defined pieces of mosaic. These algorithms can significantly reduce the production of a 2D (vector) condition databases of the floor mosaic for conservation applications.

To demonstrate this application, 0.75 square meter sections of mosaic flooring at Caesarea were digitized at a lateral (x and y) resolution of .5 mm and a depth resolution of 0.1 mm (Figure 2).

Figure 2a: The Large Field of View Laser Scanner mounted on a tripod to scan floor mosaics at Caesarea.

Figure 2b: The high level of detail recorded by the scanner documents the pattern layout of the tiles as well as missing tiles as shown in the intensity (b) and shape (c) images.

Figure 2c: The high level of detail recorded by the scanner documents the pattern layout of the tiles as well as missing tiles as shown in the intensity (b) and shape (c) images.

Figure 2d: The deformation by a footstep is recorded in (d) and (e).

Figure 2e: The deformation by a footstep is recorded in (d) and (e).

For more information see Godin et al, 2002. Active Optical 3D Imaging for Heritage Applications, NRC 44945.