From photogrammetry to iPad Pro in Archaeology

Excavating sites and collecting stratigraphic information are destructive and unrepeatable processes since it is impossible to re-excavate the same area and retrieve the same data. As such, creating a solid and secure archaeological record is the most crucial task for all archaeologists. However, the retrieved data has changed through time, from scarce fieldnotes and unclear sketches to the current meticulous and detailed information about the observed realities with the taking of samples, draws and photos.

In recent times, the application of new technologies in Archaeology has been an increasing reality, facilitating and improving our work. One of the most notorious examples is photogrammetry. This tool also allows for a more complete, reliable, and long-lasting archaeological record, creating 3D models that can be revisited after the excavation and disseminated and communicated in interactive ways.

But what is photogrammetry? With this technique, and with the right software, it is possible to overlap, digitally, lots of 2D photographs and turn them into 3D models by reproducing the geometry of objects/plans through the examination of series of images (either from satellites, drones, planes, or conventional cameras). Due to the development of more user-friendly software, which has significantly reduced the requirements of hardware and technical expertise needed to capture images and produce quality three-dimensional models correctly, this has become a viable tool. Still, the processing time (depending on the number of photos could reach up to 24h) and the dimension of the generated models (with no less than 1GB) obliged many archaeologists to update their computers or overloaded designers who collaborate with them.

However, a new tool has been emerging since 2020 – The LiDAR sensor installed in both the iPad Pro and iPhone pro.

Tiago do Pereiro, from ERA Arqueologia and also a collaborator in some ICArEHB projects, using iPad Pro in the excavation of a megalithic Monument (photo taken from ERA Arqueologia Facebook)

LiDAR or Light Detection and Ranging use a pulsed laser to measure ranges (variable distances). These light pulses generate precise 3D information about the shapes with which they contact and their surface characteristics.
On the Apple devices, the LiDAR Scanner can measure the distance to surrounding objects up to 5 meters away, working both indoor and outdoor. Combined with proper software and the right app, the LiDAR Scanner will gain data from both cameras and motion sensors on the iPad, producing, in just a few minutes (due to its powerful GPU), 3D models that can be projected (using augmented reality) into the world.

To Archaeology, this tool can allow a widespread usage of 3D models, a more accurate record and increase the reproducibility and communicative potential of our interventions, but also reduce costs, decrease the error in the 3D models (since the processing is done on-site and mistakes can be easily corrected) and increase productivity.

In the Walled Enclosure of Santa Vitória, during the 2021 fieldwork, all 3D models and drawings were done using the latest iPad Pro 2021, which allowed us to have all the graphic documentation completed by the end of the campaign. Still, one of the first users of this new tool was ERA Arqueologia, who also collaborates with ICArEHB.

Author: Ana Catarina Basílio

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