Conventionally, in photogrammetry, photographs of an existing building are taken; the images are then scanned into a computer.  From the scanned images the computer can dimension the building to within an accuracy of a few millimeters.  For inverse-photogrammetry, we start with photographs of a site where buildings once stood, then reconstruct the building or buildings within the computer.

The process, as applied to the monuments of Gebel Barkal, proceeded as follows.  In 1989, Dr. Timothy Kendall, assistant curator at the Museum of Fine Arts, Boston, provided Riseman with 3-D coordinate data that was shot using a 3-D laser transit.  With the use of additional plans and field diaries, some dating back to 1910, Riseman created 2-D vector plans which were subsequently extruded up into the third dimension.  From that information he constructed an accurate 3-D wireframe model of the entire site. 
 

He then digitally composited the 3-D wireframe onto site photographs to verify accuracy.  The wireframe computer reconstructions of the temples of Gebel Barkal were subsequently rendered into a solid model which was then transposed back onto the scanned photograph for a complete view of the (simulated) original temple in its original topographic setting.  The scene was enhanced further through the addition of people, trees, and mudbrick buildings to heighten the illusion of seeing an actual 3000-year-old scene.

Such visual transpositions and such archaeological insight could not be accomplished through any other medium with such accuracy, nor with the added benefit of being able quickly and efficiently to test various reconstructed environments for the best archaeological fit.

This was our first pass at reconstructions of the buildings at Gebel Barkal.  In 1995, a second model was built (focusing on Temple B700), which was subsequently recoded for virtual reality. Work then moved to Temple B300, as LEARNING SITES moves to re-create the entire ancient religious center.