Point cloud vs drawing on archaeological site

摘要

Archaeology is a discipline closely related to the representation of objects that are at the center of its concerns. At different times of the archaeological method, representation approach takes different forms. It takes place on the archaeological excavation, during the exploration, or in a second time in the warehouse, object after object. It occurs also in different drawing scales. The use of topographical positioning techniques has found its place for decades in the stratigraphic process. Plans and sections are thus readjusted to each other, on the excavation site. These techniques are available to the archaeologist since a long time. The most of the time, a qualified member of the team performs himself these simple topographical operations. The two issues raised in this article are: three-dimensional acquisition techniques can they, first find their place in the same way on the excavation site, and is it conceivable that it could serve to support the representation? The drawing during the excavations is a very time-consuming phase; has it still its place on site? Currently, the drawing is part of the archaeological stratigraphy method. It helps documenting the different layers, which are gradually destroyed during the exploration. Without systematic documentation, any scientific reasoning cannot be done retrospectively and the conclusions would not be any evidence. Is it possible to imagine another way to document these phases without loss compared to the drawing? Laser scanning and photogrammetry are approved as acquisition techniques. What can they bring more to what is already done for archaeologists? Archaeological practice can be seen as divided into two parts: preventive archeology and classical archeology. The first has largely adopted the techniques that provide point clouds to save valuable time on site. Everything that is not destroyed by the archaeological approach will be destroyed by the building construction that triggered the excavations. The practice of classical archeology by academics is less governed by the on-site timesaving. The excavation is also the place of the transmission of knowledge and the time spent is beneficial to students. But experimenting with the production of point clouds by archaeologists of emergency can influence the practices of archeology as a whole. An experiment is ongoing on the Saint-Hilarion Monastery site in the Gaza Strip. Each layer of a stratigraphic excavation area was documented by photogrammetry. This project was the means to transfer knowledge related to photogrammetry to allow the archaeologist to document the stratigraphic layers one after the other. Indeed it is essential that this documentation is systematic and not dependent on the availability of specialist in photogrammetry. The risks related to possible wrong practices of photogrammetry by archaeologist are identified, and solutions are proposed. Monitoring means of photogrammetric missions must be established to allow complete and usable documentation. The methods implemented are already applied on other archaeological sites and help save precious time on site.