The survey work at Pompeii, the first phase of the larger project to study the forum, began in early June of 1994. Pompeii Forum Project Director and University of Virginia Professor John J. Dobbins, CSA Director Harrison Eiteljorg, II, University of Wisconsin at Stevens Point Professor Larry Ball, and architect Karim Hanna met in Rome and drove to Pompeii, beginning work there on June 6.
The Architecture School of the University of Virginia permitted Professor Dobbins to borrow a Topcon total station for use at Pompeii. The instrument included an electronic transit (for measuring angles) and an electronic measuring device (EDM) for measuring the distance from the machine to a reflecting prism. It did not include a data storage device for recording the information, as the total station made its measurements and calculations. Therefore, information generated by the instrument was recorded by hand in the field. (We used a cumbersome system to prevent error. Each piece of information was spoken by the instrument operator to the recorder and repeated back by the recorder. Only single digits were spoken to try to minimize errors; so the number 321.456 would have been pronounced, "three two one point four five six," not, "three hundred twenty-one point four fifty-six." Occasionally, the recorder intentionally mis-stated the numbers to make certain that the instrument operator was fully attending. Despite that care, one set of coordinates was found to have been transposed during the process of working on the files.) Although this was slow and tedious, and clearly not as desirable as using a data recorder to automate the process, it did work. It also meant that we relied less on automation and therefore were somewhat more self-conscious about the processes used.
We intended to do direct surveying of both ground plans and standing architecture with the total station and to use the photogrammetry features built into AutoCAD to survey standing remains more completely. AutoCAD includes the capacity to use photographs of flat, single-plane surfaces - even photographs taken from oblique angles - and to trace details on those surfaces directly from the photograph into the drawing as if one were tracing from a scaled plan, and we planned to use that process as well as conventional surveying techniques. (An article describing the photogrammetry work and illustrating some of the results will appear in the November issue of the Newsletter.)
To take full advantage of the photographs with AutoCAD, a medium format camera was taken to Pompeii, a 6 cm. by 7 cm. Mamiya RB67, with both normal and wide-angle lenses. The larger negatives, compared to 35 mm. negatives, permit sharper enlargements and, consequently, greater accuracy in the orientation and tracing processes. We used black-and-white film only for this work (cost being the major determinant), but color could be used, and, indeed, color prints from any of the slides taken at the site could be used if desired.
The first order of business was to begin the survey of the forum with a starting point and some datum points to which we could refer as we moved the transit about the area.
We then surveyed individual areas more carefully, using the methods described elsewhere in this issue. We were able to survey the west face of the Sanctuary of the Genii of Augustus and the interior of the western two spaces of the sanctuary. We augmented survey information with hand measurements in some cases, e.g., the altar of the Sanctuary.
For the individual interior spaces, using photographs for additional survey information made it possible to add considerable detail and to make extensive surface models of those spaces. It will also be possible to use the photographs to model the walls more completely, separating the earlier and later phases as well as differing construction techniques.
After working on the Sanctuary of the Genii of Augustus, we moved to the Imperial Cult Building next door. In that case we worked only to obtain as good a ground plan as possible.
Professor Dobbins had previously submitted an article about the building, and a new drawing for that article was ready, to be plotted before we left Pompeii.
Although we were able to work for only two weeks, a great deal was accomplished, thanks to the use of the total station, and a good deal more work can be done away from the site with AutoCAD and the photographs taken in Pompeii.
For other Newsletter articles concerning the applications of CAD modelling in archaeology and architectural history or Pompeii, consult the Subject index.
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