Research released on Monday in the Journal of Archaeological Science may lead to whole chapters of Cambodia’s history being rewritten. 
 
 The results of the most extensive airborne laser-scanning campaign ever conducted on an archaeological project show that the city of Angkor may not have been abandoned in the 15th century due to a Siamese attack and occupation, as previously believed. 
 
 Khmer kings may have relocated in the course of political upheavals, but ground surface scans do not show thousands of people following them, writes Australian archaeologist Damian Evans in the article. 
 
 “It now seems plausible that an illusion of premodern mobility and urban disjuncture has been created by episodes of fusion and fission of authority among different royal houses…and may not, in fact, have involved the physical ‘movement’ of anything much at all, let alone radical demographic shifts, or entire cities being carved ex nihilo from the wilderness,” he writes. 
 
 A research fellow at the French School of Asian Studies (EFEO) based in Siem Reap City, Mr. Evans conducted the Cambodian Archaeological Lidar Initiative (CALI) in March and April 2015. Flying over 1,910 square km of Cambodia, he collected data with remote-sensing technology—known as Lidar—that penetrates forests and vegetation, gathering information about the soil’s surface and enabling archaeologists to find out whether land in a given area was ever disturbed by human activity. 
 
 The information collected will take years to analyze. But already, it has provided information that may force researchers to reassess the idea that the Angkorian empire collapsed in the early 15th century. 
 
 “In spite of the dubious nature of the evidence for the sacking of Angkor, and regardless of evidence for the continued vitality of Angkor and Cambodia in the post-Angkorian period…the period between the late 13th to early 15th centuries is now associated with the kind of dramatic demographic decline at Angkor implied by the word ‘collapse,’” Mr. Evans writes. 
 
 If this were the case, the landscape would reflect the sudden movement of hundreds of thousands of people away from Angkor and toward post-Angkorian capitals; but so far, there is no evidence of such massive migration, he said. 
 
 These preliminary findings are quite exciting, historian David Chandler wrote in an email on Sunday night. 
 
 “The people who built and worshipped in the temples have joined the temples to give us a complex, intriguing picture of Angkor as an inhabited site instead of as a mysterious monumental space,” he wrote. 
 
 This offers a vision of the population—estimated at about 1 million people—actually using and managing waterworks and roads, even after their kings had left, added Mr. Chandler, one of the foremost historians on Cambodia. 
 
 The CALI project was supported by Cambodia’s government and a long list of international organizations and universities involved in archaeological research in the country. This was the second Lidar campaign—the first one, in 2012, was also led by Mr. Evans. 
 
 It now will take years to analyze the data and conduct field research based on the findings, Mr. Evans wrote in an email on Sunday night. 
 
 “We know very well today that humans are profoundly altering the surface of the planet and strongly influencing global systems such as climate and so on; I think perhaps what we hadn’t realized before was the extent that this also took place in the distant past, although of course on a more limited and localised scale, but with equally challenging consequences for societies in antiquity,” he said. 
 
 “It’s a very exciting time to be an archaeologist, and perhaps the most exciting time in the history of aviation to be an aerial archaeologist.” 
 
 vachon@cambodiadaily.com 
 
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 The Journal of Archaeological Science is aimed at archaeologists and scientists with particular interests in advancing the development and application of scientific techniques and methodologies to all areas of archaeology. This established monthly journal publishes focus articles, original research papers and major review articles, of wide archaeological significance. 
 
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 Please see our Guide for Authors for information on article submission. If you require any further information or help, please visit our Support Center ||||| New findings by archaeologists reportedly reveal the scale of medieval cities hidden under the jungle, near the pictured Angkor Wat temple, to be significantly bigger than was previously known Unprecedented new details of medieval cities hidden under jungle in Cambodia near Angkor Wat have been revealed using lasers, archaeologists said Sunday, shedding new light on the civilisation behind the world's largest religious complex. 
 
 While the research has been going on for several years, the new findings uncover the sheer scale of the Khmer Empire's urban sprawl and temple complexes to be significantly bigger than was previously thought. 
 
 The research, drawing on airborne laser scanning technology known as lidar, will be unveiled in full at the Royal Geographic Society in London on Monday by Australian archaeologist Damian Evans. 
 
 "We always imagined that their great cities surrounded the monuments in antiquity," Evans told AFP. 
 
 "But now we can see them with incredible precision and detail, in some places for the very first time, but in most places where we already had a vague idea that cities must be there," he added. 
 
 Angkor Wat, a UNESCO World Heritage site seen as among the most important in southeast Asia, is considered one of the ancient wonders of the world. 
 
 It was constructed from the early to mid 1100s by King Suryavarman II at the height of the Khmer Empire's political and military power and was among the largest pre-industrial cities in the world. 
 
 But scholars had long believed there was far more to the empire than just the Angkor complex. 
 
 'Entire cityscape' 
 
 The huge tranch of new data builds on scans that were made in 2012 that confirmed the existence of Mahendraparvata, an ancient temple city near Angkor Wat. 
 
 But it was only when the results of a larger survey in 2015 were analysed that the sheer scale of the new settlements became apparent. 
 
 To create the maps, archaeologists mounted a special laser on the underneath of a helicopter which scans the area and is able to see through obstructions like trees and vegetation. 
 
 Much of the cities surrounding the famed stone temples of the Khmer Empire, Evans explained, were made of wood and thatch which has long rotted away. 
 
 "The lidar quite suddenly revealed an entire cityscape there with astonishing complexity," he said. 
 
 "It turned out we'd been walking and flying right over the top of this stuff for ten years and not even noticing it because of the vegetation." 
 
 Among the new scans already published are a detailed map of a huge city complex surrounding the stone temple known as Preah Khan of Kompong Svay, a series of iron smelting sites dating back to the Angkor era and new information on the complex system of waterways that kept the region running. 
 
 The new data also maps out the full extent of Mahendraparvata, information that will make future digs much more accurate and less time consuming. 
 
 "What we had was basically a scatter of disconnected points on the map denoting temple sites. Now it's like having a detailed street map of the entire city," Evans said. 
 
 Further maps will be published in the coming months, he added. 
 
 Long Kosal, a spokesman for the Apsara authority, the government body that manages the Angkor complex, said the lidar had uncovered "a lot of information from the past." 
 
 "It shows the size and information about people living at those sites in the past," he told AFP, adding further research was now needed to capitalise on the finds. 
 
 While the Khmer Empire was initially Hindu it increasingly adopted Buddhism and both religions can be seen on display at the complex. 
 
 Angkor is visited by hundreds of thousands of visitors a year and remains Cambodia's top tourist attraction. 
 
 Explore further: New discoveries redefine Angkor Wat's history ||||| Exclusive: Laser technology reveals cities concealed under the earth which would have made up the world’s largest empire in 12th century 
 
 Archaeologists in Cambodia have found multiple, previously undocumented medieval cities not far from the ancient temple city of Angkor Wat, the Guardian can reveal, in groundbreaking discoveries that promise to upend key assumptions about south-east Asia’s history. 
 
 The Australian archaeologist Dr Damian Evans, whose findings will be published in the Journal of Archaeological Science on Monday, will announce that cutting-edge airborne laser scanning technology has revealed multiple cities between 900 and 1,400 years old beneath the tropical forest floor, some of which rival the size of Cambodia’s capital, Phnom Penh. 
 
 Some experts believe that the recently analysed data – captured in 2015 during the most extensive airborne study ever undertaken by an archaeological project, covering 734 sq miles (1,901 sq km) – shows that the colossal, densely populated cities would have constituted the largest empire on earth at the time of its peak in the 12th century. 
 
 Evans said: “We have entire cities discovered beneath the forest that no one knew were there – at Preah Khan of Kompong Svay and, it turns out, we uncovered only a part of Mahendraparvata on Phnom Kulen [in the 2012 survey] … this time we got the whole deal and it’s big, the size of Phnom Penh big.” 
 
 Laser technology reveals lost city around Angkor Wat Read more 
 
 A research fellow at Siem Reap’s École Française d’Extrême-Orient (EFEO) and the architect of the Cambodian Archaeological Lidar Initiative (Cali), Evans will speak at the Royal Geographic Society in London about the findings on Monday. 
 
 Evans obtained European Research Council (ERC) funding for the project, based on the success of his first lidar (light detection and ranging) survey in Cambodia in 2012. That uncovered a complex urban landscape connecting medieval temple-cities, such as Beng Mealea and Koh Ker, to Angkor, and confirmed what archaeologists had long suspected, that there was a city beneath Mount Kulen. It was not until the results of the significantly larger 2015 survey were analysed that the size of the city was apparent. 
 
 That survey uncovered an array of discoveries, including elaborate water systems that were built hundreds of years before historians believed the technology existed. The findings are expected to challenge theories on how the Khmer empire developed, dominated the region, and declined around the 15th century, and the role of climate change and water management in that process. 
 
 “Our coverage of the post-Angkorian capitals also provides some fascinating new insights on the ‘collapse’ of Angkor,” Evans said. “There’s an idea that somehow the Thais invaded and everyone fled down south – that didn’t happen, there are no cities [revealed by the aerial survey] that they fled to. It calls into question the whole notion of an Angkorian collapse.” 
 
 The Angkor temple ruins, which sprawl across the Unesco-protected Angkor archaeological park, are the country’s top tourist destination, with the main temple-city, Angkor Wat, appearing on the Cambodian national flag. Considered the most extensive urban settlement of pre-industrial times, and boasting a highly sophisticated water management system, Angkor’s supposed decline has long occupied archaeologists. 
 
 Archaeologists discover massive Petra monument that could be 2,150 years old Read more 
 
 The new cities were found by firing lasers to the ground from a helicopter to produce extremely detailed imagery of the Earth’s surface. Evans said the airborne laser scanners had also identified large numbers of mysterious geometric patterns formed from earthen embankments, which could have been gardens. 
 
 Experts in the archaeological world agree these are the most significant archaeological discoveries in recent years. 
 
 Michael Coe, emeritus professor of anthropology at Yale University and one of the world’s pre-eminent archaeologists, specialises in Angkor and the Khmer civilisation. 
 
 “I think that these airborne laser discoveries mark the greatest advance in the past 50 or even 100 years of our knowledge of Angkorian civilisation,” he said from Long Island in the US. 
 
 Facebook Twitter Pinterest There is an undiscovered city beneath Mount Kulen. Photograph: Terence Carter 
 
 “I saw Angkor for the first time in 1954, when I wondered at the magnificent temples, but there was nothing to tell us who had lived in the city, where they had lived, and how such an amazing culture was supported. To a visitor, Angkor was nothing but temples and rice paddies.” 
 
 Charles Higham, research professor at the University of Otago in Dunedin, New Zealand, and the leading archaeologist of mainland south-east Asia, said it was the most exciting paper he could recall reading. 
 
 “I have been to all the sites described and at a stroke, they spring into life … it is as if a bright light has been switched on to illuminate the previous dark veil that covered these great sites,” Higham said. “Personally, it is wonderful to be alive as these new discoveries are being made. Emotionally, I am stunned. Intellectually, I am stimulated.” 
 
 David Chandler, emeritus professor at Monash University in Melbourne, Australia, the foremost expert on Cambodian history and the author of several books and articles on the subject, said the work was thrilling and credited Evans and his colleagues with “rewriting history”. 
 
 
 
 Chandler said he believed it would open up a series of perspectives that would help people know more about Angkorian civilisation, and how it flourished and eventually collapsed. 
 
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 “It will take time for their game-changing findings to drift into guide books, tour guides, and published histories,” Chandler said. “But their success at putting hundreds of nameless, ordinary, Khmer-speaking people back into Cambodia’s past is a giant step for anyone trying to deal with Cambodian history.” 
 
 David Kyle, an archaeologist and ecological anthropologist has conducted projects at Phnom Kulen, the location of the biggest findings, the massive city of Mahendraparvata, the size of Phnom Penh, beneath the forest floor. 
 
 He said the “survey results have revolutionised our understanding and approaches. It’s impossible not to be excited. It facilitates a paradigm shift in our comprehension of the complexity, size and the questions we can address.” 
 
 While the 2012 survey identified a sprawling, highly urbanised landscape at Greater Angkor, including rather “spectacularly” in the “downtown” area of the temple-city of Angkor Wat, the 2015 project has revealed a similar pattern of equally intense urbanism at remote archaeological ruins, including pre- and post-Angkorian sites. 
 
 Dr Peter Sharrock, who is on the south-east Asian board at London University’s School of Oriental and African Studies and has a decades-long connection to Cambodia, said the findings showed “clear data for the first time of dense populations settled in and around all ancient Khmer temples”. 
 
 “This urban and rural landscape, linked by road and canal networks, now seems to have constituted the largest empire on earth in the 12th century,” Sharrock said. 
 
 Evans, whose domain is an air-conditioned room full of computers at the French archaeological centre in Siem Reap, rather than dirt trenches at far-flung digs, is modest about his achievements and quick to credit his colleagues on the Cali project. 
 
 Facebook Twitter Pinterest A fight scene depicted in detail in the bas-reliefs at the Banteay Chhmar temple complex. Photograph: Terence Carter 
 
 He said he believed the discoveries would completely upend many assumptions about the Khmer empire. He also hoped it would bring the study of people back into the picture. 
 
 Coe, who has been to many of the places covered by the survey and has seen the imagery, said that while the 2012 survey of Phnom Kulen demonstrated what the technology could do – “it could look through the dense jungle covering these hills and reveal an unexpected city which predated Angkor itself” – the 2015 survey took this into new dimensions. 
 
 This view was shared by Dr Mitch Hendrickson, the director of the industries of Angkor project and assistant professor in the department of anthropology at the University of Illinois. He said the initial survey had been “an incredible leap forward” in archaeologists’ ability to see everything for the first time and had been “a major game-changer” in understanding how the Angkorian Khmer people built, modified and lived in their cities. But he was “stunned” by the second survey. 
 
 “The results for Preah Khan of Kompong Svay are truly remarkable and are arguably the jewel in the crown of this mission. The lidar shows us that there was much, much more,” Hendrickson said, referencing a full-blown community layout that was previously unknown. “It’s both humbling and exciting. There are so many fantastic new discoveries.” 
 
 “We knew that Preah Khan of Kompong Svay was significant before the lidar – it’s the largest complex ever built during the Angkorian period at 22 sq km, it is connected to Angkor directly by a major road fitted with infrastructure, and likely played a role in facilitating iron supply to the capital. 
 
 
 
 Facebook Twitter Pinterest The team at Siem Reap’s École Française d’Extrême-Orient look at a map of the site. Photograph: Terence Carter 
 
 “The new results suggest that it may have been more important than many temples built in Angkor and that it had a decent-sized population supporting it.” 
 
 Dr Martin Polkinghorne, a research fellow in the department of archaeology at Adelaide’s Flinders University who is conducting a joint research project on Longvek and Oudong, the post-Angkorian capitals, said his team would use the data during excavations scheduled until 2019 to understand the cities. 
 
 “The decline of Angkor is among the most significant events in the history of south-east Asia, but we do not have a precise date for the event,” Polkinghorne said. “By using lidar to guide excavations on the capitals of Cambodia that followed we can determine when the kings of Angkor moved south and clarify the end of Angkor. 
 
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 “Cambodia after Angkor is customarily understood in terms of loss, retreat and absence; a dark age,” he said. “Yet, Cambodia was alive with activity after Angkor. South-east Asia was the hub of international trade between east and west. Using the lidar at Longvek and Oudong in combination with conventional archaeology we will reveal the dark age as equally rich, complex and diverse.” 
 
 What is a lidar survey? 
 
 An airborne laser scanner (ALS) is mounted to a helicopter skid pad. Flying with pre-determined guidelines, including altitude, flight path and airspeed, the ALS pulses the terrain with more than 16 laser beams per square metre during flights. The time the laser pulse takes to return to the sensor determines the elevation of each individual data point. 
 
 The data downloaded from the ALS is calibrated and creates a 3D model of the information captured during the flights. In order to negate tree foliage and manmade obstacles from the data, any sudden and radical changes in ground height are mapped out, with technicians who have models of the terrain fine-tuning the thresholds in processing these data points. Once completed, the final 3D model is handed over to the archaeologists for analysis, which can take months to process into maps.
– All is not as it has seemed in Cambodia, according to new research published in the Journal of Archaeological Science. Using aerial scanning technology that determines precise elevation points beneath even dense jungle foliage, archaeologists say they have uncovered multiple metropolises between 900 and 1,400 years old that might have made up the largest empire on the planet at the time, reports the Guardian. The findings also upend a key chapter in the history of Southeast Asia. Historians have long thought that the city of Angkor was abandoned in the 15th century amid a Siamese attack and occupation, but the research finds no evidence to suggest that a million people uprooted themselves in a mass migration, reports Cambodia Daily. Instead, it appears that the population remained and thrived, boasting complex waterway systems that emerged centuries earlier than thought. "What we had was basically a scatter of disconnected points on the map denoting temple sites," lead archaeologist Damian Evans of Australia tells AFP. "Now it's like having a detailed street map of the entire city." He says more maps will be published in the months ahead, but his second round of scans, which were taken in 2015 after the first round in 2012, has his peers abuzz. "It is as if a bright light has been switched on to illuminate the previous dark veil that covered these great sites,” says New Zealand archaeologist Charles Higham. "It is wonderful to be alive as these new discoveries are being made." The technology, called Lidar, forms a 3D model of any stark changes in ground height. The maps illustrate just how extensively developed the area was around Angkor Wat, a UNESCO World Heritage site. (See why this underwater find isn't a lost city after all.)