Seeing the Big Picture with LiDAR

Oct 18, 2016

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Seeing the Big Picture with LiDARThe LiDAR images in the last Lab Note show how this technology can be used to map large structures through thick tropical foliage. Those scenes represent a tiny fraction of the El Pilar Archaeological Reserve for Flora and Fauna, however, which extends for 20 square kilometers on both sides of the Belize/Guatemala border. To understand the big picture of settlement survey that forms the basis of this project, we have to look beyond the "downtown" area to see where else people were building structures and living. A complete LiDAR map of the Reserve is the perfect place to start.

                
 
(North is Up)
 This map contains a lot of information, and we will go over the important features, step by step. The first item to note is the quadrilateral shape marked out with a solid black line: this marks the boundary of the Reserve. You can see that the LiDAR survey actually encompasses a slightly larger area, but our current investigations are confined to this protected archaeological zone. Next, you will see a double-cluster of black features slightly to the right of center, which are the monumental buildings of  "downtown" El Pilar that we presented in the previous Lab Note. The Citadel is visible just to the right of this area, across a ravine and outlined in black. Slightly to the left of center is an additional cluster of black-outlined civic structures called Pilar Poniente; this group is connected to the "downtown" area by a large sacbe, or causeway, which is also outlined in black. The map also shows the topography of the Reserve, with dark reds representing higher elevations that grade through oranges and yellows to greens, which represent low-lying areas and seasonal swamps.
Click on the image to open a larger version in a new window. Take a few minutes to zoom in on different areas of the map, and you may begin to see features that look like tiny hills or bumps on the landscape. Many of these are ancient structures, which appear as overgrown mounds if you are lucky enough to see them through the dense forest cover, but some may be natural features, such as large ant hills or cohune palm debris piles. If you spot several of these features formally arranged around an open space, you have almost certainly discovered the patio  group of an ancient Maya household. A good place to look is in the upland areas around the monumental structures. Look a while longer at the map, and you may begin to notice that the dark red and green areas contain far fewer recognizable structures. These are the broken hilltops and swampy lowlands - areas where we would not expect many people to live.
We will take a closer look at the low-lying green areas in the next Lab Note. To date, we have found few traces of ancient buildings on the steep hillslopes in the southwest of the Reserve, probably because it would be exceedingly difficult to build there. But our surveys show that people built structures in the lowland swampy areas, and we aim to discover their purpose through more intensive investigations.

Li Dar

El Pilar

Survey

Jennifer and Sherman Horn II like this.

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Jennifer EmeryBacker

Are the formations made of easily accessible stone? Are they intricate enough to show a large artistic group of workers? Are any human remains from war/ invasion found scattered about? And your best as to the demise of the civilization

Oct 20, 20160

Sherman Horn IIIResearcher

Large structures at El Pilar are faced with limestone masonry blocks that were probably quarried from the ridge-lands around the center. Smaller structures, like the houses and other buildings that most people used, were made of perishable materials that haven't survived. Luckily for us, many smaller buildings were set on stone-faced platforms to raise them above the ground, and we find their remains as mounds of debris with stone alignments at their bases. We don't have good evidence for dedicated groups of architects or architectural artists as yet, but the scale and quality of construction suggests a specialized knowledge of how to build big, impressive monuments. Where, and in whom, architectural and construction knowledge was stored by the ancient Maya remains and interesting question. No evidence of war or invasion yet, although this is notoriously difficult to discover even at sites with unquestionably defensive fortifications. It's possible that excavations around the Citadel would turn up some clues, but we're not even sure that it was used for community defense at this point. As far as how El Pilar fit in with the broader "Maya Collapse," I can't tell yet. The center appears to have been abandoned, like many others in the Southern Maya Lowlands, probably sometime after AD 900 at the end of the Classic period. But there are some big issues with saying that kind of thing, because there hasn't been a lot of work done on what might be there from later times. I doubt that the area was depopulated as some people suggest, and we have some evidence of later architecture, but on a much smaller scale. At the very least, the political institutions did fail, and the tradition of divine kings was replaced by some other form of organization.

Oct 24, 20160

Jennifer EmeryBacker

Oct 20, 20160

Jennifer EmeryBacker

What are the dotted lines? Approx how many inhabitants do you surmise? Was this a society with distinct classes?

Oct 18, 20160

Sherman Horn IIIResearcher

Great questions! The large dotted lines are modern roads that run through the Reserve. You can see that the one running through the monumental core corresponds to the north-south white line in the map in our previous Lab Note. Your next two questions are more difficult to answer. Estimating ancient Maya populations is tricky - anyone who tells you differently has not thought deeply about the problem or is trying to pull the wool over your eyes! That's because they are estimates that are based on samples, although they are often presented as if a census of the ancient population were taken. Anabel Ford has been working in the area for around 30 years, and she has developed a number of population estimates that account for things like landforms, soil types, the probability that all households dated to a certain period weren't actually occupied at the same time (especially when a period lasts for 300 years!), and the possibility that all these "residential" mounds weren't the primary residences of families. We don't have a revised estimate based on our LiDAR data yet - we're still field-checking those results - but an earlier estimate of over 20,000 people may be accurate. Dr. Ford has also estimated that between 176,000 - 182,000 people lived in the surrounding 1,288 square kilometers of the upper Belize Valley. More accurate population models and estimates is one of our primary goals for doing this research! As for distinct classes: well, yes, there do seem to be class divisions between people we might consider nobles and commoners, but it's a bit more nuanced than that. There probably were different "levels" of status within each of these groups, and we really don't know how rigid the boundary was between the two. We don't know who, if anyone, was able to own land, and we don't fully understand the relationships of production and consumption among the inhabitants of ancient Maya cities. These are questions many of us are working to address, but any definitive answers will depend on the accumulation of a lot more research from many different sites.

Oct 19, 20160

About This Project

People of the Swamp: LiDAR and "Invisible" Structures at El Pilar

University of California, Santa Barbara/Mesoamerican Research Center

Aerial LiDAR surveys have been popular tools for mapping ancient Maya settlements through the dense rainforest canopy. LiDAR mapping at El Pilar revealed several previously unknown large structures, but many smaller structures in low, swampy areas were invisible to this technique. This project will develop a program of field-checking LiDAR anomalies to clarify the patterns of small structures in seasonal swamps, where settlement models predict people would not live.