Vol. XII, No. 3
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Winter, 2000

Propylaea Project Gets Back In Gear

The next phase of the Propylaea Project, delayed multiple times for a variety of reasons, will begin in February. Mr. Eiteljorg will go to Athens to work with Mary Ioannidou, the structural engineer who works with Dr. Tasos Tanoulas on the Propylaea and who will be in charge of the actual modeling. Ms. Ioannidou has taken an AutoCAD® course and is prepared to begin the modeling. She has been able to set aside about 10 days for working on the model; so Mr. Eiteljorg will join her for that period, and the two of them will develop the procedures to be used. In this phase of the project Mr. Eiteljorg and Ms. Ioannidou intend to develop and refine the CAD processes with which Ms. Ioannidou will create the full model. (The building of the model may be done principally by others working with AutoCAD under Ms. Ioannidou's direction in Athens.)

There are several issues of importance that will need to be decided. One, of course, is the layer-naming system to be applied. It will be based on the CSA Layer Naming Convention, http://csa.brynmawr.edu/web1/csalnc.html (currently www.csanet.org/inftech/csalnc.html - 11 July 2000) discussed elsewhere in this issue ("CAD Data Segmentation - A Crucial Tool"), but it will be tailored specifically to the Propylaea. Ms. Ioannidou and Mr. Eiteljorg will have to decide how to deal with different phases and alterations, for instance, as well as with such uncertainties as building fragments that cannot be precisely and certainly positioned in the original structure. The problems will be exacerbated by the numerous modifications to the structure, with blocks having new cuttings or surface treatments long after the original work was completed.

A set of procedures for the actual modeling must also be developed. The work on the Propylaea has heretofore been documented with standard drawings. Those drawings have been made according to the highest standards of architectural and archaeological drafting; they are much more than dry records and often rise to the level of works of art. The CAD model will be much different. The drawing is not the real product; the need to produce exquisite pen-and-ink individual drawings is not paramount. Instead, the CAD model will be designed to record all details - perhaps not in graphically beautiful ways, but accurately - and to make three-dimensional views easy and accurate. For instance, cracks, abrasions, scratches, and other surface defacements will be included in the CAD model, but probably not as the carefully drawn hatching, shading, and the like used in drawings.

One possibility for recording such surface features is using digital photographs and including the photographs in the CAD model. A photograph can be attached to a given stone so that the photo of the stone appears as its surface when requested. Mr. Eiteljorg will take along a digital camera for that purpose and some experiments with that process will be undertaken.

Similarly, the need to show subtle shapes in CAD - something rather easy to do in drawings - will be a challenge (see the simple example in the last issue of the Newsletter, Vol XII, No. 2, Fall, 1999, "Using CAD on an Archaeological Site,"). As difficult as it may be to make such a drawing in two dimensions, it is much more difficult to do so while working in three dimensions.

Another question that will arise is how to deal with geometrically complex shapes such as Ionic capitals and even column entasis. Although the depiction of entasis may depend upon the way dimensions have been taken, there is virtually no reasonable way to model each Ionic capital in full. It may be necessary to use photographs in conjunction with CAD shapes or to create a single Ionic capital based on one sample from the building and adjust only its size to match the remains of the other capitals.

These are the kinds of questions that will be confronted in this phase of the project - and that, when answered, will make the following phase possible.

For other Newsletter articles concerning the applications of CAD modeling in archaeology, or CSA/ADAP projects, consult the Subject index.

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