In order to increase the accuracy of our data, the speed with which we do our work, and the information discovered about the past, we are incorporating cutting edge techniques and developing our own new techniques to document the archaeology. Here are some of the techniques we currently use:
REFLECTANCE TRANSFORMATION IMAGING (RTI)
Rock inscriptions at Wadi el-Hudi were originally made using two different techniques. First a person could “carve” an inscription by repeatedly tracing specific lines on a stone surface with another sharp stone or chisel. Alternatively, a person would “peck” an inscription, by repeatedly striking the rock until enough of its surface chipped off to form an image. Both techniques offer challenges in recording. At Wadi el-Hudi, we have used RTI to document the inscriptions on the rock outcrops and boulders in the desert, as well as artifacts and stelae collected during survey and excavation. RTI is a new and simple technology, developed by Cultural Heritage Imaging. This technique uses a series of photographs taken from the same perspective with different angles of light. With these photographs, RTI software can be used to develop a “reflectance” model of the photographed surface. The technique creates a file that allows us to view the surface while manipulating the angle of light. For copying inscriptions (a.k.a. epigraphy), the reflectance model also yields quantitative information about the physical surface of the stone on which the inscription was carved. For rock art, this model gives a specific measure of the degree of smoothing of a surface that has resulted from the pecking technique for making an inscription. This is a measure that can determine the amount of time that a carver spent on a particular inscription or area in it. Traditional, drawing-based epigraphy, which does not measure the degree of smoothing, can depict a pecked surface only with variable degrees of stippling in the drawing of the inscription. But the quantitative information which RTI provides is extremely important for publishing these inscriptions because every nuance adds to their correct translation, recording, and historical interpretation. As an innovation for working at Wadi el-Hudi, we have had to devise portable dark-rooms to aid in capturing the right lighting conditions for RTI on rock-inscriptions. Members of the team also innovated techniques to derive automatic epigraphic drawings from a photographed surface. Similarly, we have also used this technique on artifacts, like pottery sherds, to show the formation techniques and decoration. RTI has already aided in identifying production techniques used in certain pots that are possibly Nubian due to their techniques of decoration.
PHOTOGRAMMETRY FOR EPIGRAPHY
In the course of our work at Wadi el-Hudi, we want to republish the 155 inscriptions previously photographed and copied by Ahmed Fakhry along with the nearly 100 new inscriptions that we have already found and the additional ones we will find in future seasons. When we do so, we want to interpret the inscriptions in their spatial and physical contexts because the meaning of an inscription can change based on how (or even if) it was visible for people to see. Thus, the epigraphic study of the inscriptions at Wadi el-Hudi has necessarily depended upon our 3D surveys of the area. The challenge of undertaking epigraphic work at Wadi el-Hudi is that the inscriptions are carved onto irregular surfaces on rocks. In the past, epigraphers documenting rock inscriptions would lay clear vellum over inscriptions like these in order to copy them. But that technique inherently distorts a 3D inscription, making it appear as a 2D drawing. Moreover, the traditional method is physically challenging, time-consuming, and expensive because a person must do the copying and collating work in the desert.
Instead, the Wadi el-Hudi team is recording the inscriptions as 3D models using photogrammetry with high-resolution digital imagery. Essentially, we take high-resolution photographs and RTI images of the inscriptions, and we map each of the inscriptions with a total station (see “Mapping and 3D Modelling” below). This allows us to make 3D models of all the inscriptions. Similarly, with this data, we digitally render the image in 2D so that we can still create traditional line drawings of the inscriptions for publication in books. But we can do so at home, out of the desert. This process is ongoing. In future seasons, we will collate our drawings with the original inscriptions to insure their accuracy.
MAPPING AND 3D MODELING
We use a LEICA total station to map most of the architecture, artifacts, excavation areas, and inscriptions at each archaeological site. The total station is an optical and electronic instrument that measures slopes and distances to a particular point from the instrument’s location (or “station”). With it, we create highly accurate maps and models of the sites. Furthermore, by mapping a series of transecting lines to geodetic benchmarks around Wadi el-Hudi that have been previously and precisely mapped, we have been able to give Universal Transverse Mercator (UTM) coordinates for all of our sites. This information allows the data to be imported into any geographic information system. That is, we can describe precisely where the sites are and convey that information to anyone. Also, using a series of photographs taken from overhead we are creating photo-mosaics of the archaeological sites as high-resolution Red-Green-Blue (RGB) maps annotated with architectural lines and topographic contours. These will become definitive published maps of most archaeological sites at Wadi el-Hudi, hopefully to appear in the near future. (And, given current threats to the site, probably the final ones ever to be made.) With this method, we have already achieved a major goal of the survey: the creation of architectural maps for 11 archaeological sites as well as the locations of all of the inscriptions at Wadi el-Hudi.
In planning beyond the print publication, we hope to find the funding to process this data and purchase server space to make it all available as a 3D model with cached photographs and annotated features on the Internet. When we return to the desert, we hope to take a series of precise photographs of those sites that have been mapped to help us create 3D models of the inscriptions and settlements for people to walk through virtually, online.
CHRONOMETRIC SURVEY TECHNIQUES
Everyone on the Wadi el-Hudi team is equipped with a Handheld, watch, and camera in addition to our notebooks. All of the photographs that we take and the notebook data are recorded with a time-stamps of the time they are being made. This allows us to produce geolocations for the photographs and notes by coordinating that data with the time that the person was in a particular location. With this information, someone walking in the desert looking for new archaeological sites automatically knows where a photograph was taken or where a note-taker stood when he or she wrote a particular note. After each day, we download the data and photographs and plot the course walked by each member of our team on GoogleEarth. With this technique, we are able to call up an area on GoogleEarth and immediately know the photo numbers of every picture taken in a specific area.
We are fortunate that Ahmed Fakhry and Ian Shaw took pictures of Wadi el-Hudi in the late 1940s and 1992 respectively. Those photos are incredibly important to our current work because we can accurately map how the archaeological sites have changed over time using a technique called Rephotography. First, we locate the exact spot and angle from which the original photograph was taken. Then we reproduce the photograph to the best of our ability according to the time-constraints and equipment that we have available. Overlaying the new photograph onto the old photograph immediately reveals features of the landscape that have changed in the intervening time. Moreover, because we know exactly where the new photo was taken and we have mapped remaining features around it, we can map the locations of any changed or missing features from the past photograph. For example, if a gate to a settlement was photographed in 1992, and it has since been bulldozed by illegal miners, we can still precisely map where the gate had been using Rephotography.
Petrography is a technique used in ceramic analysis that allows us to look microscopically at clay to understand where pottery originally came from and even give us clues on how pottery was made. In this technique, we cut a 0.3 mm thin section from a pot, mount it on a slide, and look at it under a cross polarizing microscope that changes the direction of light, enabling us to see the minerals, rocks, and organic matter that make up the clay fabric. This information helps us piece together the geological origin of clay, so that we can track where pots came from and where they went; essentially, allowing us to map ancient trade and supply routes. At Wadi el-Hudi, petrography is very important because almost all the pottery that contained vital supplies was imported into the site. Understanding the geological origin of the pottery can help us learn about who supplied food and water to the miners in the desert.
Cross polarizing microscope at the Institut français d'archéologie orientale in Cairo, where Meredith Brand analyzes Wadi el-Hudi pottery