Documentation of the hypostyle hall of the great temple of Amon-Re in Karnak Egypt – A pharaonic project
For the thousands of daily visitors who discover the great dynastic temple of Amon-Re in Karnak, the hypostyle hall is undoubtedly the most spectacular part of the monument. This immense room of more than 5000m², built at the time of Seti I in the 13th century BC, is the support of a very dense epigraphy, whose colors are often saved. The ceiling is supported by 12 central columns with a diameter of 3m rising to 20 meters and 122 side columns 13 meters high and a diameter of 2m50.
However, as famous as it is, the great hall remains poorly documented: until recently, there was no exhaustive photographic survey of the decor, necessary for a detailed analysis. Part of this gap was filled in the last century by a major photographic survey campaign. However, to complete this documentation, it remained to treat the columns.
After a first 3D scanning operation 10 years ago, a complete photogrammetric coverage was carried out in 2008. In order to produce orthophotos with a 2.5mm pixel (over an area of nearly 15,000 m2), the columns were covered by nearly 4500 convergent metric photographs taken with an 8 meter pole. The shooting and its exploitation proved to be very complex, because of the geometric constraints (small space between the columns, continuity of the visits) and radiometric (photography of each sector of the columns at different periods to avoid the direct lighting).
These medium-resolution orthophotos make it possible to see at a glance the entire surface of the columns. It is mainly useful for architectural studies, and can also be used as atlas for epigraphic data. But its resolution is insufficient for the epigraphic study itself, and especially for the search for palimpsests, that is to say the traces of decorations or inscriptions prior to the last state of the hypostyle hall, that several pharaoh of the XXIXth Dynasty (notably Ramses II) have recapured.
To achieve this goal, it was necessary to specify a much higher resolution shooting. Together with the Egyptologists of the team, after several tests of legibility on test zones, we chose a pixel size of 0.25 mm (while being aware that this would represent a work 100 times higher than the average resolution that we had already had so much trouble carrying out …). At first, only the engraved scenes representing the deities were treated, a height of about 3m30. Each column portion concerned was photographed by 7 rings of 16 images, made by artificial lighting (flashes) from a telescopic scaffolding (the area to be treated being relatively close to the ground). The georeferencing of these images was obtained by measuring characteristic points from the medium resolution models. The photography operations are now complete, and the calculation of the orthophotos is programmed according to the priorities of the Egyptologists.
But there remained a undocumented part of the edifice, and indeed even virtually unknown: the higher parts, above the capitals, the abacuses, architraves and claustra, barely visible from the ground, and nevertheless decorated as carefully as the rest of the building. Access, where it is possible, is very dangerous, and because of the collapse of the ceilings, many areas are completely inaccessible (at least since the beginning of the XX century, when the room was backfilled to allow the reassembly of columns collapsed in 1899).
Fortunately, the 2017 mission has been authorized to use a drone to photograph in a very detailed way the upper parts of the room, with systematic horizontal and vertical shots. Thirty flights of 20 minutes (battery life) were performed every morning at the same time, the time when the direction of the sun changes the least (and incidentally where the tourist flow is the lowest). All these flights were made a few meters from the masonry, in manual control, space congestion making predefined flight plan to dangerous. Needless to say, the pilot’s task was tough! This very exhaustive campaign (in intervallometric mode, a photo every 2 seconds) has enabled the acquisition of twenty thousand images, whose georeferencing is ensured by a re-installation of the markup of the network of 2008, visible on vertical axis images.
The meeting of all these sources of documentation acquired over the last ten years can now serve as a basis for architectural, historical and epigraphic research.
This mission gathered in Karnak in December 2017:
- Owen Murray (Canada), photographer, drone pilot
- Emmanuel Laroze (France, CNRS) architect
- Yves Egels (France, IGN / ENSG) photogrammetre
as part of the Great Hypostyle Hall project.