[UPDATE: Please check the comments for Damian Evans’ friendly critiques of my comments]
I first visited Angkor in 2005 as a tourist (following a couple months of survey in southern Cambodia). If you’ve visited Angkor perhaps you, like me, stared out from your tuk-tuk as you breezed pass the thick trees in Angkor Thom and wondered “I wonder what is going on in there?” You might also have recognized that at its height, Angkor and its many temples would not be the vacant ceremonial center that it appears today, but a bustling city and so you might have also wondered “Where were all these people living?”
I did not know then that a French archaeologist, Jacque Gaucher, had spent the better part of 20 years hacking through the thick forests of Angkor Thom, mapping the mounds and features there and identifying the city and its ancient grid system. He has produced a detailed map of that city, but the decades it took to put together meant that to create similar maps of the rest of Angkor would take several lifetimes.
Walking around the forested parts of Angkor, you can tell that these areas are not empty spaces. You can spot ceramics on the surface and you can see the undulations on the ground that indicate the presence of mounds and depressions (some of which may be ponds).
In 2010 (before we had LIDAR data) my Greater Angkor Project colleagues tried to map some of the mounds and depressions we saw within the Angkor Wat enclosure. You can see from the top image below (taken from our recent Antiquity publication) that my colleagues had figured out a rough pattern. However, due to the dense tree cover it was extremely difficult to see the broader grid system within the enclosure. Nor were we aware that this orthogonally organized mound-depression pattern extended outside the eastern moat of Angkor Wat, to an area we have referred to as the External Eastern Enclosure (it is bounded by a rectangular earthwork).
This, my friends, is the magic of LIDAR.* What would have taken many people many years of survey work (ground and aerial) and archaeological mapping can instead be achieved in just a few minutes of survey with LIDAR. And with this we can clearly see the detailed landscape modifications surrounding temples, connecting urban spaces and waterways, and even buried sandstone quarries. We can see how much the Angkorians (and we are learning, the pre-Angkorians) extensively planned and managed their landscapes.
However, LIDAR is not the culmination of our research on Angkor but a new beginning point. With these data we now have clearer picture of, for example, where people are living. (This in particular has been the inspiration for my research to more intensively excavate and investigate house mounds). The LIDAR data has provided a detailed map and with this, new questions arise and has the potential to launch many new research projects. It is a tool to help is focus on more specific and more productive research questions, but it is not the answer in itself.
In fact, there is quite a lot that Lidar cannot do. For example:
-Lidar cannot tell us that everything we find is an archaeological site. For this, we need to – boots on the ground – visit and verify that the site is archaeological. This is called ground-truthing. This is part of some of the ongoing work by my colleagues associated with the Cambodian Archaeological Lidar Initiative.
-Lidar cannot tell us what all the features are. There are quite a few enigmatic sites (geometric shapes that may be gardens and the “mound fields” to name two), which must be investigated with on the ground archaeological work in order to determine their nature and function.
-Lidar cannot tell us how old a feature is. For this we need to go out and visit a site specifically – perhaps even undertaking an excavation in order to get datable material. Although some materials on the surface (diagnostic ceramics, for example) can give us an idea of how old something is.
-Lidar cannot necessarily tell us how these features relate to one another. Lidar picks up modifications to the landscape, but because many of these features may have been constructed at different times, we need archaeological research to understand how they are connected (or not) to one another.
-Lidar cannot tell us what is under the ground. For this, we need archaeological investigations or other remote sensing techniques like ground-penetrating radar.
The Lidar data is magic, but knowledge is produced when combining this with scientific, archaeological research.
In the next post, I’ll discuss some of the finds in the forthcoming Lidar publication in a bit more detail.
*I was not directly involved in this project, but have benefitted from the results and work with several members of CALI.