In addition to the traditional methods used by archeologists to study buildings, including taking comprehensive and detailed photographs and studying ancient documents and drawings, archeologists Martin and Birthe Biddle and their colleagues employed a number of sophisticated scientific techniques to examine the Church of the Holy Sepulchre and the edicule that purportedly houses the Tomb of Christ.
A 3D photogrammetric survey of the edicules
The primary technology used in their survey of the site was photogrammetry, which allows researchers to create two- or three-dimensional images of a structure from any vantage point. The data from which the images are constructed comes from conventional or digital photographs. Not just any photographs, however; they have to include small, reflective “targets” stuck on walls or other surfaces with adhesive. The targets have cross-hairs, which allow their exact location to be measured with a surveying tool called a theodolite. From the location of the targets, an imaginary coordinate grid is constructed in and around the entire site — within the edicule of the Church of the Holy Sepulchre, for example. “When you take your photographs you have, preferably, four of these targets in each one,” says Martin Biddle. The photographs are taken in “stereopairs,” overlapping images that, when viewed in a certain way, form a three-dimensional image of an object. “The stereopairs are set up in a photogrammetric plotter with the coordinate values you know from your survey. Thereafter, you can plot any point in the stereo image in terms of that coordinate grid. You know the x and y and z axes — up and down and sideways,” Biddle explains. “Once you have that data in, you can instruct the machine to print out a view looking up from underneath, or down from above — whatever way you want.”
To probe the interior of the edicule, beneath what could be seen photographically, the Biddles and their colleagues used a technique called thermography, which uses special heat-detecting (thermographic) cameras to detect minute variations in temperature. “The police and armed forces use this with aerial cameras to find the body heat of hidden bodies or of people trying to infiltrate across areas, for example,” explains Biddle. It can also be used in buildings like the Church of the Holy Sepulchre, because the various materials out of which the structures are constructed will release heat at different rates — rock slower than wood, say. “In the case of the Holy Sepulchre,” Biddle says, “we hypothesized that there might be a different rate of cooling between the block containing the tomb chamber within the rock and the block in front of it, the area known as the Chapel of the Angel” — where a fragment of the rolling stone that covered the entrance to Christ’s tomb is said to lie. “And indeed, that is what we found. The images show that one side — the tomb side–is slightly redder, slightly hotter.”
Finally, to get an up-close look at what’s inside the walls of the edicule, the researchers used an endoscope — essentially, a narrow tube containing optical fibers and with a light on the end, attached to some sort of viewing device. Endoscopes are commonly used in medical procedures, say, during laparoscopic or arthroscopic surgery. The endoscope was fed through the cracks in the outer skin of the edicule. “What we saw was that the outer skin is really a skin. It is not attached to the core, and that core is composed of a very different kind of material. We could be seeing the outer surface of the original rock tomb,” Biddle says. The endoscope also revealed that the outer edicule is falling away from the walls of the building that is underneath — the earlier edicule — “which accounts for the present very bad state of the structure,” Biddle says.
