Finding Lost Cities with Lidar
How does laser scanning make ancient settlements under forests visible? A short story of digital archaeology.
Translated from the Turkish original: Türkçesini oku
IN SHORT
Lidar maps the ground beneath the forest canopy with laser pulses sent from an aircraft. More than 60,000 Maya structures in Guatemala, an urban fabric at Angkor and low-density urbanism in the Bolivian Amazon have come to light with this method.
The biggest obstacle in archaeology was not really the cost of excavation but a problem of seeing: detecting settlements under dense forest cover. Lidar (light detection and ranging) changed this problem at its root.
How does it work?
From an aircraft or a drone, hundreds of thousands of laser pulses per second are sent towards the forest. Some of the pulses bounce off the leaves, and some reach the ground. When the signals returning from the ground are filtered and combined into a point cloud, the trees are virtually “erased” and the topography beneath is laid bare: roads, terraces, plazas, canals.
What has been found
Which ancient settlements have been found with lidar?
Scans of northern Guatemala, carried out in 2016 and published in 2018, revealed more than 60,000 structures, settlements and lines of defence in the Maya region. In Cambodia, a whole urban fabric surrounding the temples around Angkor became visible. In the Bolivian Amazon, platform mounds, raised causeways and water channels point to low-density urbanism under the forest. Data collected in a few flights opened up areas that decades of fieldwork could not see.
Discovery or verification?
We need to be careful here: a “lost city” was often never lost to local communities; it simply had not been put on maps. Lidar’s contribution is not finding something new but lifting the cover and making claims measurable. There is also an ethical dimension: detailed published maps can become road maps for looters too. As the speed of discovery increases, so does the responsibility to protect.
The next step is clear: point cloud classification supported by artificial intelligence, in which the machine recognises patterns among billions of points that the human eye cannot see. The laser has taken the place of the spade; nothing has yet taken the place of interpretation.
References
- Canuto, M. A., Estrada-Belli, F., Garrison, T. G., Houston, S. D., Acuña, M. J., Kováč, M., Marken, D., Nondédéo, P., Auld-Thomas, L., Castanet, C., Chatelain, D., Chiriboga, C. R., Drápela, T., Lieskovský, T., Tokovinine, A., Velasquez, A., Fernández-Díaz, J. C., & Shrestha, R. (2018). Ancient lowland Maya complexity as revealed by airborne laser scanning of northern Guatemala. Science, 361(6409), eaau0137. https://doi.org/10.1126/science.aau0137
- Chase, A. F., Chase, D. Z., Weishampel, J. F., Drake, J. B., Shrestha, R. L., Slatton, K. C., Awe, J. J., & Carter, W. E. (2011). Airborne LiDAR, archaeology, and the ancient Maya landscape at Caracol, Belize. Journal of Archaeological Science, 38(2), 387–398. https://doi.org/10.1016/j.jas.2010.09.018
- Evans, D. H., Fletcher, R. J., Pottier, C., Chevance, J.-B., Soutif, D., Tan, B. S., Im, S., Ea, D., Tin, T., Kim, S., Cromarty, C., De Greef, S., Hanus, K., Bâty, P., Kuszinger, R., Shimoda, I., & Boornazian, G. (2013). Uncovering archaeological landscapes at Angkor using lidar. Proceedings of the National Academy of Sciences, 110(31), 12595–12600. https://doi.org/10.1073/pnas.1306539110
- Prümers, H., Jaimes Betancourt, C., Iriarte, J., Robinson, M., & Schaich, M. (2022). Lidar reveals pre-Hispanic low-density urbanism in the Bolivian Amazon. Nature, 606(7913), 325–328. https://doi.org/10.1038/s41586-022-04780-4
