Until recently, archaeology was limited by what a researcher could see while standing on the ground. But light detection and ranging, or lidar, technology has transformed the field, providing a way to scan entire regions for archaeological sites.
With an array of airborne lasers, researchers can peer down through dense forest canopies or pick out the shapes of ancient buildings to discover and map ancient sites across thousands of square miles. A process that once required decades-long mapping expeditions, and slogging through jungles with surveying equipment, can now be done in a matter of days from the relative comfort of an airplane.
But lidar maps are expensive. Takeshi Inomata, an archaeologist at the University of Arizona, recently spent $62,000 on a map that covered 35 square miles, and even was deeply discounted. So he was thrilled last year when he made a major discovery using a lidar map he had found online, in the public domain, entirely for free.
The map, published in 2011 by Mexico’s National Institute of Statistics and Geography, covered 4,440 square miles in the Mexican states of Tabasco and Chiapas. It was made as part of the institute’s mission to create accurate maps to be used by businesses and researchers.
Dr. Inomata learned about the map from Rodrigo Liendo, an archaeologist at the National Autonomous University of Mexico. The resolution of the map was low. But the outlines of countless archaeological sites stood out to Dr. Inomata. So far, he has used it to identify the ruins of 27 previously unknown Maya ceremonial centers that contain a type of construction that archaeologists had never seen before. These sites may hold insights into the origins of Maya civilization.
“We can see a much better picture of the entire society,” Dr. Inomata said.
His findings have not yet been peer-reviewed, but Dr. Inomata has presented his work at four conferences during the past year. “The stuff he is finding is crucial for our understanding of how Maya civilization developed,” said Arlen Chase, an archaeologist at Pomona College, who did not contribute to Dr. Inomata’s work.
Dr. Chase was among the early adopters of lidar. In 2009, he used it to map Caracol, a Maya city in Belize, where he and Diane Chase, an archaeologist at Claremont Graduate University, have worked for 35 years. The two are married, and their son, Adrian, a Ph.D. candidate at Arizona State University, is now using lidar to compare the square footage of more than 4,000 homes in Caracol as a way to infer social inequality. (Presumably then, as now, wealthier residents had larger homes.) Such an analysis would have been all but impossible before lidar.
The Maya civilization arose between 1,000 B.C. and 400 B.C. When Dr. Inomata first began studying the Maya as a graduate student in the 1980s, his professors were mainly interested in the Classic Period, between A.D. 250 and A.D. 900, when the Maya were at their political and economic peak. Dr. Inomata was more interested in how Maya culture began, and the artifacts that could answer his questions were buried even deeper underground.
Years passed before he had enough grant money, and a sufficiently secure academic appointment, to start that project. Finally, in 2005, he and his wife, Daniela Triadan, an anthropologist at the University of Arizona, began excavating the ancient city of Ceibal in the Petén rainforest in Guatemala, where they discovered some of the earliest known Maya buildings. The city’s ceremonial center dates to 950 B.C., but Ceibal didn’t have permanent housing until 200 years later.