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Laser Technology Reveals Surprising New Features at Angkor

Laser Technology Reveals Surprising New Features at Angkor


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Utilising the latest cutting-edge technology, archaeologists studying Angkor Wat in northwestern Cambodia have made some surprising new findings , most significantly that the ancient Khmer Empire capital was much larger than previously thought.

Angkor, the famous capital of southeast Asia’s largest ancient empire, has been intensively studied by archaeologists over the decades, so much so that it was not thought that there was much left to find. But latest research has shown that the ancient city had many more secrets to reveal.

Led by archaeologist Damian Evans of the University of Sydney, Australia, a research team applied high-tech LiDAR (Laser Interferometry Detection and Ranging) scanning to gain a visual representation of the landscape of Angkor Wat below the heavily forested areas. What they found was remarkable.

“We found that this nicely formally planned grid extends for 35 square kilometres, rather than the 9 kilometres that had previously been mapped from the ground,” said Evans. “Angkor has been considered to be (among the) cities enclosed by moats or walls, but we found that the town area of the city grids extends far beyond the moat spaces.”

These results indicate that the city would have been capable of supporting a population of 750,000 to one million inhabitants, and at 35 square kilometres, the city covered an area the size of New York – an impressive feat in the ninth century.

A second highly significant finding to come out of LiDAR’s ability to create a precise map of the hidden city, was that Angkor was an incredibly well thought out city . The streets ran in a grid exactly east/west or north/south. Each city block was measured exactly 100 meters by 100 meters, with 4 dwellings and 4 rectangular ponds, each pond located north-east of each dwelling. The dwellings, elevated on earthen mounds, were higher than the surrounding rice fields, presumably so they wouldn’t flood during the rainy season. The roads were likewise elevated.

Other peculiar findings include a series of features which appear to be embankments, but layered out in a spiral pattern. At this stage it is unclear exactly what they were used for.

The implication of this research is that archaeologists may now have important clues regarding one of the biggest mysteries shrouding the ancient city – how Angkor met its end. “They overused the land and probably caused a great amount of erosion, clogged up the canals and the whole irrigation system would have collapsed,” said Evans. Scholars now theorize that as the city’s population grew, it became increasingly more difficult for the surrounding agriculture to support the urban population.


    Beyond Angkor: How lasers revealed a lost city

    Deep in the Cambodian jungle lie the remains of a vast medieval city, which was hidden for centuries. New archaeological techniques are now revealing its secrets - including an elaborate network of temples and boulevards, and sophisticated engineering.

    In April 1858 a young French explorer, Henri Mouhot, sailed from London to south-east Asia. For the next three years he travelled widely, discovering exotic jungle insects that still bear his name.

    Today he would be all but forgotten were it not for his journal, published in 1863, two years after he died of fever in Laos, aged just 35.

    Mouhot's account captured the public imagination, but not because of the beetles and spiders he found.

    Readers were gripped by his vivid descriptions of vast temples consumed by the jungle: Mouhot introduced the world to the lost medieval city of Angkor in Cambodia and its romantic, awe-inspiring splendour.

    "One of these temples, a rival to that of Solomon, and erected by some ancient Michelangelo, might take an honourable place beside our most beautiful buildings. It is grander than anything left to us by Greece or Rome," he wrote.

    His descriptions firmly established in popular culture the beguiling fantasy of swashbuckling explorers finding forgotten temples.

    Today Cambodia is famous for these buildings. The largest, Angkor Wat, constructed around 1150, remains the biggest religious complex on Earth, covering an area four times larger than Vatican City.

    It attracts two million tourists a year and takes pride of place on Cambodia's flag.

    But back in the 1860s Angkor Wat was virtually unheard of beyond local monks and villagers. The notion that this great temple was once surrounded by a city of nearly a million people was entirely unknown.

    It took over a century of gruelling archaeological fieldwork to fill in the map. The lost city of Angkor slowly began to reappear, street by street. But even then significant blanks remained.

    Then, last year, archaeologists announced a series of new discoveries - about Angkor, and an even older city hidden deep in the jungle beyond.

    An international team, led by the University of Sydney's Dr Damian Evans, had mapped 370 sq km around Angkor in unprecedented detail - no mean feat given the density of the jungle and the prevalence of landmines from Cambodia's civil war. Yet the entire survey took less than two weeks.

    Lidar - a sophisticated remote sensing technology that is revolutionising archaeology, especially in the tropics.

    Mounted on a helicopter criss-crossing the countryside, the team's lidar device fired a million laser beams every four seconds through the jungle canopy, recording minute variations in ground surface topography.

    The findings were staggering.

    The archaeologists found undocumented cityscapes etched on to the forest floor, with temples, highways and elaborate waterways spreading across the landscape.

    "You have this kind of sudden eureka moment where you bring the data up on screen the first time and there it is - this ancient city very clearly in front of you," says Dr Evans.

    These new discoveries have profoundly transformed our understanding of Angkor, the greatest medieval city on Earth.

    At its peak, in the late 12th Century, Angkor was a bustling metropolis covering 1,000 sq km. (It would be another 700 years before London reached a similar size.)

    Angkor was once the capital of the mighty Khmer empire which, ruled by warrior kings, dominated the region for centuries - covering all of present-day Cambodia and much of Vietnam, Laos, Thailand and Myanmar. But its origins and birthplace have long been shrouded in mystery.

    A few meagre inscriptions suggested the empire was founded in the early 9th Century by a great king, Jayavarman II, and that his original capital, Mahendraparvata, was somewhere in the Kulen hills, a forested plateau north-east of the site on which Angkor would later be built.

    But no-one knew for sure - until the lidar team arrived.

    The lidar survey of the hills revealed ghostly outlines on the forest floor of unknown temples and an elaborate and utterly unexpected grid of ceremonial boulevards, dykes and man-made ponds - a lost city, found.

    Most striking of all was evidence of large-scale hydraulic engineering, the defining signature of the Khmer empire.

    By the time the royal capital moved south to Angkor around the end of the 9th Century, Khmer engineers were storing and distributing vast quantities of precious seasonal monsoon water using a complex network of huge canals and reservoirs.

    Harnessing the monsoon provided food security - and made the ruling elite fantastically rich. For the next three centuries they channelled their wealth into the greatest concentration of temples on Earth.

    One temple, Preah Khan, constructed in 1191, contained 60t of gold. Its value today would be about £2bn ($3.3bn).

    But despite the city's immense wealth, trouble was brewing.

    At the same time that Angkor's temple-building programme peaked, its vital hydraulic network was falling into disrepair - at the worst possible moment.

    The end of the medieval period saw dramatic shifts in climate across south-east Asia.

    Tree ring samples record sudden fluctuations between extreme dry and wet conditions - and the lidar map reveals catastrophic flood damage to the city's vital water network.

    With this lifeline in tatters, Angkor entered a spiral of decline from which it never recovered.

    In the 15th Century, the Khmer kings abandoned their city and moved to the coast. They built a new city, Phnom Penh, the present-day capital of Cambodia.

    Life in Angkor slowly ebbed away.

    When Mouhot arrived he found only the great stone temples, many of them in a perilous state of disrepair.

    Nearly everything else - from common houses to royal palaces, all of which were constructed of wood - had rotted away.

    The vast metropolis that once surrounded the temples had been all but devoured by the jungle.

    Watch the first episode of Jungle Atlantis on Thursday 25 September at 20:00 BST on BBC Two, or catch it later on the BBC iPlayer. The programme was made in association with The Smithsonian Channel, which will be transmitting both episodes in the US on 5 October under the title Angkor Revealed.


    A window into the past

    Sometimes the earth reveals them voluntarily, sometimes they are found by chance and often they are searched for - archaeological riches. Excavation sites around the world offer fascinating insights into the origins of our cultures.

    Travel tips for fans of archaeology


    Laser vision reveals hidden worlds

    Some of the central pyramids of ancient Caracol in Belize. Laser mapping showed that at its peak, this Mayan metropolis sprawled over an area the size of present-day Washington, D.C.

    Dennis Jarvis / Flickr (CC BY-SA 2.0)

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    In the ancient Maya city of Caracol, map-making can be treacherous. Jungles shroud this site in the Central American nation of Belize. Dense shrubs stand taller than a person’s head. They hide ruins that otherwise would be obvious. To reveal the city, archeologists must hack through the growth, using sharp blades called machetes. They step carefully to avoid critters like the fer-de-lance, a common viper with an often-fatal bite.

    Arlen and Diane Chase know these hazards well. These archeologists work at the University of Central Florida in Orlando. For three decades, the husband-and-wife team (who cut their wedding cake with a machete) also have patiently studied Caracol. Season by season, they and their team — and later, their children — have hacked and mapped, hacked and mapped.

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    Then, in April 2009, everything changed. That’s when lidar came to Caracol. Lidar stands for “light detection and ranging.” It’s a method of using lasers to create a map. And it revealed this part of the world in a whole new light.

    Explainer: What are lidar, radar and sonar?

    For five days, a small Cessna airplane buzzed over Caracol and the surrounding region. Onboard, a device fired laser pulses at the ground. And not just a few: This machine sent billions of pulses streaming into the jungle.

    Some laser pulses vanished in the heavy tree cover. Many others bounced off leaves and returned to the plane. Still others reflected off of the ground or hidden stone structures. The lidar device recorded how long it took the echo of each pulse to return. The device used those bounce times to compute how far the light had traveled. In total, it recorded more than 4 billion measurements of the jungle terrain.

    Back on the ground, computer programs turned those data into a detailed map of the site. The laser pulses revealed the contours of temples and other buildings, roadways and even terraced fields. It was as if lidar had peeled back the jungle to reveal much more of Caracol than anyone had seen since the Maya city went into decline more than 1,000 years ago.

    Arlen Chase said that all at once he could “see” the jungle-covered ruins he and Diane had painstakingly charted over the decades. This map also turned up many other hidden archeological features. “I couldn’t stop looking at it,” he says. “It was mind-boggling.”

    From underground to outer space

    Laser-built maps can reveal ruins hidden for centuries. And not only in Belize. Elsewhere around the world, lidar projects have been uncovering other hidden treasures. These observations are inspiring scientists to question what they thought they knew about how ancient civilizations lived.

    Nor is archeology the only field getting a boost from lasers. Scientists use lidar anywhere a map might be useful, from high above Earth to deep below. Some experts have been charting clouds and gases in the atmosphere with lidar. Others have probed deep dark caves and the changing shapes of coastlines. The technology even has been used to map the surfaces of Mars, Mercury and the moon.

    “There’s no other way to collect this kind of data,” says Andrew Fountain. A geologist at Portland State University in Oregon, Fountain has used lidar to map changes in ice-free deserts in Antarctica.

    Laser pulses sent out from a plane created this digital map of one of the McMurdo Dry Valleys. National Center for Airborne Laser Mapping funded by NSF The strategy behind lidar is simple. Beam out a bunch of light pulses and record those that bounce back. The same idea underlies other sensing technologies, such as radar and sonar.

    Radar devices emit invisible radio waves. Those waves that bounce back reveal the location or speed of distant objects. That is why police officers use radar guns to scout for speeders among passing cars.

    Similarly, sonar devices emit sounds and listen for echoes. This method even works underwater, where sound travels farther than light or radio waves. Some animals have naturally developed a type of sonar. Both bats and dolphins can “see” in dim places by producing sounds and listening for echoes. This natural sonar is called echolocation.

    In the 1970s, NASA missions used lidar to study Earth’s atmosphere. In the early 21 st century, the precision of laser mapping increased and its costs dropped. Early lidar instruments fired 3,000 pulses per second of one color. Newer ones emit 900,000 pulses per second and use multiple colors. Different colors of laser light penetrate or reflect off of materials differently. So multiple lidar beams could capture more information. For example, multiple-beam data might show the types of trees and other plants in a forest.

    Today, scientists can use these systems to explore hidden structures almost anywhere. At about the same time, global positioning systems, or GPS, have made it possible to link the laser maps to specific locations.

    Expanding horizons

    The Chases began their work at Caracol in 1985. That was long before lidar was an option. Back then, textbooks described this site as a small settlement that had played a minor role in Maya history. Gradually, the Chases started turning up hints that Caracol was much bigger than those textbooks had suggested. They found roadways leading away from the center of the ruins. They found an inscription, carved into rock, that told of the city’s history — and boasted of triumphs over powerful neighbors.

    Year by year, the Chases and their team built a case that Caracol was once a powerful and important Maya capital.

    “Hardly anybody believes it when they wander the countryside,” says Arlen Chase. “We had been telling our colleagues for years” that Caracol was much bigger than it looks. “But we couldn’t demonstrate it.”

    This image was created using laser pulses fired from an airplane at the ground beneath. It shows some of the ruins at Caracol. A. and D. Chase, Caracol Archaeological Project, www.caracol.org The 2009 lidar project finally delivered the solid evidence that Caracol had been a sprawling metropolis. The Chases had initially estimated Caracol covered some 23 square kilometers (about 9 square miles). The lidar data suggested the city was far, far bigger — roughly 177 square kilometers (68.3 square miles). That is the size of Washington, D.C.

    The researchers used lidar to map the terraced fields that fed the estimated 115,000 people who lived in Caracol. The maps also revealed roadways and reservoirs no one even knew had existed.

    Ancient cities in the tropics

    With lidar mapping, Caracol quickly morphed from a mid-size village to a major “city in the tropics,” says Arlen Chase. And before long, researchers elsewhere trained lidar on a host of other sites in Central America.

    A 2013 study in Honduras spotted ruins that some speculate may be part of a legendary lost city known as La Ciudad Blanca. That year brought a second lidar survey of Caracol. It mapped more than 1,000 square kilometers (386 square miles), including much of the area surrounding the city. That survey shows that Caracol was even larger than the Chases had thought. The original city probably spilled over into what is today Guatemala.

    A helicopter equipped with a lidar system flies over Angkor Wat, Cambodia, in April 2012. The mapping system revealed new details about the ancient site. Francisco Goncalves/PT McElhanney Lidar technology is simply “eye-opening,” says John Weishampel. He’s an ecologist at the University of Central Florida who often works with the Chases. If you want to map a site like Caracol from the ground, he notes, “you’re talking decades.” But survey it from the air using lidar, he says, and the same things can be mapped with “probably two weeks of flight time and three weeks of [computer] processing.”

    These Florida scientists are now analyzing the Caracol data for insights into the ancient Maya civilization. Arlen Chase says their latest map offers an even better sense of how the city fit within the larger Maya landscape. The Maya empire was one of the most advanced ancient civilizations in the Americas. At its peak about 1,400 years ago, its network of cities occupied parts or all of southern Mexico, Belize, El Salvador, Guatemala and Honduras.

    On the Indochina Peninsula, half a world away, another major lidar project is underway. It’s probing the temples of Angkor Wat. Built in the 12 th century, these are among the best-known landmarks of Cambodia. They marked the capital of a large empire that thrived between the 9 th and 15 th centuries. In the 600 years since then, forest has reclaimed much of what was once among the world’s largest cities.

    In April, 2012, researchers used lidar to create this map of the area around Angkor Wat, a temple complex in Cambodia. The map showed parts of the ancient metropolis that haven’t been explored or studied. Damian Evans Archeologist Damian Evans works at the University of Sydney in Australia. In 2012, he led a lidar survey of the region surrounding the temples. (He even rode on the helicopter as it swept over the area.) Ground-based fieldwork in this part of Southeast Asia can be perilous. Land mines, for instance, lurk in some of the areas he’s studying.

    Using lidar data covering 370 square kilometers (about 180 square miles), he and his colleagues found that ancient city was — as at Caracol — much larger than researchers had believed. It also hosted a far bigger population. The map showed how the city was organized using a grid system. It also revealed the traces of farmed terraces and long-lost rice fields. All had been hiding beneath the heavy tree cover.

    “The more information we get from the lidar data, the deeper our understanding of the civilization,” Evans says. “Temples and inscriptions, which are informative on certain aspects, are frustratingly silent on a range of other issues we are interested in.” Examples include learning more about how the people changed the landscape and how they made use of natural resources.

    Evans has planned a second lidar study of the region later this year. It’s slated to survey an additional 1,600 square kilometers (about 620 square miles). The new study will help scientists better understand not only what the city looked like but also how it functioned. Lidar can reveal irrigation networks, for example, that supplied water to grow crops.

    Lasers in the valley of the dead

    The McMurdo Dry Valleys of Antarctica are the opposite of the lush jungles at Angkor Wat and Caracol. They are a frigid desert. They’re also a hotbed of lidar research.

    The wide valleys lie beneath icy mountain peaks. The largest ice-free patches on the continent, these valleys cover an area almost four times as large as the city of Los Angeles. These desolate deserts are unlike anywhere else on Earth, observes Fountain, the Portland State geologist.

    “It’s kind of like Death Valley or other deserts in the southwestern United States, but there are no plants,” he notes. “It’s cold, and glaciers reach in from the surrounding mountainsides.” The sun never rises very high in the sky. As a result, long shadows often stretch from the peaks across the valleys. The valley colors are stark: The sky is blue, the mountain peaks white and the ground a medium brown. Gravel blankets the valley floors. This can make walking there frustrating, like stumbling along a rugged beach, Fountain explains.

    Researchers have been using lidar to study changes in the McMurdo Dry Valleys, in Antarctica. This photo shows a field camp. Peter West/National Science Foundation After probing these valleys for more than a decade, Fountain recently brought lidar into his research. The National Center for Airborne Laser Mapping conducted the laser surveys of Caracol. In February 2015, experts from this government-supported research center flew a small Twin Otter airplane equipped with a laser-mapping device over the McMurdo Dry Valleys.

    Fountain’s lidar survey of this area won’t reveal the secrets of any ancient civilization. But it might just tell scientists something about the future. He suspects the valley floors are sinking. To find out, he wants to compare the new lidar data with those collected by a NASA lidar study in 2001.

    Much of the ice in Antarctica is left over from the last ice age, which ended more than 10,000 years ago. As Antarctica’s ice sheet shrank, it left behind vast stretches of ice in the valley. Over time, Fountain says, those layers of ice became covered by sediment, or rocks, sand and other material. Someone walking in the valley today wouldn’t notice the ice underneath. Over the past 10 years, however, Fountain has kept a keen eye on the buried ice. He’s seen it undergo change. Year by year, he has watched as a river cut like a knife through the underlying ice. It is a sign, he says, that the buried ice layer may be melting.

    He says the sinking doesn’t seem to be connected to global warming. Indeed, temperatures in the valley have cooled in the last few decades. He expects the valley floors to sink even more, though, if surface temperatures here do climb. Using lidar to measure these changes, no matter their cause, can help him forecast how the valleys will respond to warming.

    Fountain says he’ll begin analyzing his data this coming fall. Already he’s heard his map may offer some unexpected detail. Other scientists have contacted him to say they were conducting research in the valleys when the lidar plane flew over. Two said they were on the toilet. When camping in the McMurdo Dry Valleys, that means sitting on a bucket in the open air. That also means Fountain’s new and precise lidar map may feature a cameo of a scientist answering the call of nature.

    “Supposedly, we’ll be able to detect these people,” he says.

    Power Words

    (for more about Power Words, click here)

    Antarctica A continent mostly covered in ice, which sits in the southernmost part of the world.

    archeology The study of human history, performed by analyzing things that ancient humans left behind, from housing materials and cooking vessels to clothing and footprints. People who work in this field are known as archeologists.

    data Facts and statistics collected together for analysis but not necessarily organized in a way that give them meaning. For digital information (the type stored by computers), those data typically are numbers stored in a binary code, portrayed as strings of zeros and ones.

    echo To bounce back. For example, sound bouncing off walls of a tunnel, and returning to their source. Radio waves emitted above the surface can also bounce off the bedrock underneath an ice sheet — then return to the surface.

    echolocation (in animals) A behavior in which animals emit calls and then listen to the echoes that bounce back off of solid things in the environment. This behavior can be used to navigate and to find food or mates. It is the biological analog of the sonar used by submarines.

    glacier A slow-moving river of ice hundreds or thousands of meters deep. Glaciers are found in mountain valleys and also form parts of ice sheets.

    global positioning system Best known by its acronym GPS, this system uses a device to calculate the position of individuals or things (in terms of latitude, longitude and elevation — or altitude) from any place on the ground or in the air. The device does this by comparing how long it takes signals from different satellites to reach it.

    global warming The gradual increase in the overall temperature of Earth’s atmosphere due to the greenhouse effect. This effect is caused by increased levels of carbon dioxide, chlorofluorocarbons and other gases in the air, many of them released by human activity.

    ice age Earth has experienced at least five major ice ages, which are prolonged periods of unusually cold weather experienced by much of the planet. During that time, which can last hundreds to thousands of years, glaciers and ice sheets expand in size and depth. The most recent ice age peaked 21,500 years ago, but continued until about 13,000 years ago.

    ice sheet The broad blanket of ice, most of it kilometers deep, that covers most of Antarctica. An ice sheet also blankets most of Greenland.

    laser A device that generates an intense beam of coherent light of a single color. Lasers are used in drilling and cutting, alignment and guidance, in data storage and in surgery.

    lidar (short for light detection and ranging) A tool to measure the shape and contour of the ground from the air. It bounces a laser pulse off a target and then measures the time (and distance) each pulse traveled. Those measurements reveal the relative heights of features on the ground struck by the laser pulses.

    Maya A native American culture developed by people who lived between 2500 B.C. and 1500 A.D. in what is now parts of southern Mexico (its Yucatan Peninsula) and Central America. At its height (between about 250 and 900 A.D.), the density of people in some Maya cities was equal to that in Medieval Europe.

    National Aeronautics and Space Administration Best known as NASA, this U.S. agency was created in 1958. Since then, it has become a leader in space research and in stimulating public interest in space exploration. It was through NASA that the United States sent people into orbit and ultimately to the moon. It has also sent research craft to study planets and other celestial objects in our solar system.

    radar A system for calculating the position, distance or other important characteristic of a distant object. It works by sending out periodic radio waves that bounce off of the object and then measuring how long it takes that bounced signal to return. Radar can detect moving objects, like airplanes. It also can be used to map the shape of land — even land covered by ice.

    sediment Material (such as stones and sand) deposited by water, wind or glaciers.

    sonar A system for the detection of objects and for measuring the depth of water. It works by emitting sound pulses and measuring how long it takes the echoes to return.

    Word Find ( click here to enlarge for printing )

    Citations

    S. Ornes. “Drones put spying eyes in the sky.” Science News for Students. November 6, 2014.

    S. Perkins. “Explainer: Understanding ice ages.” Science News for Students. October 17, 2014.

    J. Weeks. “Nature's coast guards.” Science News for Students. August 16, 2014.

    D. Fox. “The oldest place on Earth.” Science News for Students. June 13, 2012.

    D. Fox. “A ghost lake.” Science News for Students. February 1, 2012.

    C.Q. Choi. “Digging into the Maya mystery.” Science News for Students. November 16, 2011.

    Original Journal Source: A. Chase et al. “Ancient Maya regional settlement and inter-site analysis: The 2013 west-central Belize LIDAR survey.” Remote Sensing. Published online September 16, 2014. doi: 10.3390/rs6098671.

    Original Journal Source: D. Evans et al. “Uncovering archaeological landscapes at Angkor using LIDAR.” Proceedings of the National Academy of Sciences. Published online July 11, 2013. doi: 10.1073/pnas.1306539110.

    About Stephen Ornes

    Stephen Ornes lives in Nashville, Tenn., and his family has two rabbits, six chickens and a cat. He has written for Science News for Students since 2008 on topics including lightning, feral pigs, big bubbles and space junk.

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    Archaeologists identify the population of the Greater Angkor region

    A pair of modern Cambodian houses: The background house is made of wood and modern materials. The house in the foreground was traditionally built of organic materials such as wood and thatched wood. International research teams have revealed where such organically constructed homes were once in the Greater Angkor area and how many people lived in each dwelling. Credit: Alison Carter

    Long-term archaeological studies, backed by aerial rider sensing and machine learning algorithms, found that 700,000-900,000 people lived in the Great Angkor region of Cambodia.

    The vast city that flourished in the 9th and 15th centuries slowly revealed to archaeologists the past hidden in the forest, but its total population was a mystery.

    The new estimates made possible by a study designed at the University of Oregon are the first of a total 3,000 square kilometers mix of urban and rural landscapes. Survey results published in the journal on May 7 Science Advances..

    Roland Fletcher, co-author of the University of Sydney and director of the Angkor Research Program, collaborative with the Cambodian Site Protection and Regional Administration, said the discovery could potentially expose cities under climate change pressure. He said it was essential to support. Angkor.

    “We mainly live in huge, low-density cities around the world, similar to Angkor, which has shown serious vulnerability to severe climate change,” Fletcher said. “We need to know how Angkor worked and what people were doing, so we can see how these experiences can refer to the risks we face in the future. You can know. “

    Combined data, including data from decades of research by international and Cambodian researchers, the new study shows Angkor’s ceremonial city centre, large cities extending outwards like modern suburbs, agriculture. We have revealed the details of the population of the embankment that incorporates the area. Angkor had a low population density and a widespread population.

    According to Fletcher, the initial estimated population was 750,000, living in an area of ​​1,000 square kilometers around central Angkor. The area is home to stone religious temples, including Angkor Wat, which attracts tourists.

    Beyond the stone temple in the center of Angkor was the location of houses and supporting structures made entirely of organic materials, all reclaimed by the jungle, said UO archaeologist Allison K. Carter.

    Carter was a co-author with Sarah Classen, a former postdoctoral fellow at the University of British Columbia. While Classen was a visiting scholar at UO with the support of the Global Oregon Faculty Collaboration Fund of the Department of International Affairs, the two planned and designed the study. A total of 14 long and active Angkor researchers collaborated.

    Klassen brings machine learning to the project and develops a multi-layered statistical analysis that merges data from historical archives and maps with details of LIDAR scans in the region in a project led by co-author Damian Evans of the French Asian Institute. Did. 2012 and 2015.

    Lidar, an abbreviation for light detection and ranging, is performed by sending a laser pulse from an aircraft to the ground. Capture ground details, ignoring the messiness of the ground, such as forests. The new data “really changed our understanding of landscapes,” Klassen said.

    Lidar has documented and mapped 20,000 previously unseen features and added them to a previous database of 5,000 locations, says Klassen, a postdoctoral researcher at Leiden University.

    “When you’re on the ground in the main part of the city center, it’s pretty forested,” Carter said. “Walking around reveals something in the surrounding landscape, but it’s not clear. Lidar provided us with a grid of beautiful mounds and depressions that seemed to be small ponds.”

    According to Fletcher, researchers at Angkor Field Station were awake and watching until early morning while the first rider image was being sent.

    “It was absolutely great,” he said. “There was previous radar data, but the amount of new information was staggering, especially as the LIDAR images captured the entire region in great detail.”

    Carter, who heads the UO’s Southeast Asian Archaeological Institute, said the new data was organized at various times in Angkor’s growth, especially during the life of the king, who had the greatest impact on infrastructure changes.

    Lidar showed where the house, built on the mound and on the stanchion, stood. The researchers estimated that each household had five people, and estimated that data to assess the total population of the area.

    “We saw the growth of the city of Angkor in chronological order,” Carter said. “We have found that different parts of the city have grown in different ways. The idea of ​​population growth in cities and suburbs today is probably the same in Angkor.”

    The results of the study will strengthen the “comparative understanding of pre-modern urbanism,” said co-author Miriam T. Stark, director of the Center for Southeast Asian Studies at the University of Hawaii at Manoa.

    “Study of Angkor’s population is important for imagining future urbanism with respect to global climate change,” Stark said. “Angkor was a tropical city that survived centuries of political and climatic change. Tracking its history and turning points is a sort of constraint for city planners to face an increase in the number of cities in the world. Helps you understand. “

    Klassen’s contribution to machine learning was first published in a 2018 survey. PLOS ONE..

    “This new treatise introduced a statistical learning paradigm and archaeological case studies and datasets, followed by statistically significant predictors of the dates of temples built in different parts of the region. To find out, we considered four classical mathematical approaches. “

    It led to a historical model of temples built during the modern years of 821-1149 within the absolute average error of 49-66.

    “This was important for our research because we could see how the metropolitan area developed compared to the ceremonial centers of the citizens,” said Classen. “We were also able to estimate the population associated with the temple and see how those populations changed over time.”

    Population information paves the way for a better understanding of Angkor’s economy and resilience, said Christophe Pottier, co-author of the French-Asia Institute, who has studied the site for 30 years.

    The growth period covered by the new survey occurred between 770 and 1300.

    Future research will look deeper into the expansion of the population cluster, according to Fletcher.

    “What was the population of Angkor before this sample period? In order to predict and model the early period, archeology must be below all current structures,” he said. ..

    The contributions of Krassen and Carter are crucial to future research, Fletcher said.

    Some of the co-authors of the new study, including Carter, Evans, and Stark, and other collaborators questioned the notion that Angkor was rapidly depopulated due to climate pressure in the 15th century.

    “From our archaeological data, it’s people who are still in the landscape, and there is evidence that the temple was modified in the 16th century,” Carter said. “Our work wasn’t designed to answer the question of when the population leaves the area, but it probably happened much slower than long thought.”

    Archaeologists are using aerial lasers to solve the mystery of the end of Angkor

    Courtesy of the University of Oregon

    Quote: Archaeologists obtained from https://phys.org/news/2021-05-archaeologists-population-greater-angkor-region.html on May 7, 2021 Greater Angkor Region (May 7, 2021) Identifies the population of the day)

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    Archaeologists identify the population of the Greater Angkor region

    Source link Archaeologists identify the population of the Greater Angkor region


    Laser Technology Reveals Surprising New Features at Angkor - History

    For the best part of 25 years, archaeologists Arlen and Diane Chase slogged through the thick undergrowth in the west of Belize in search of an ancient city whose details had been lost to the passage of time and the decay of the jungle.

    The going was tough, often requiring a machete to clear a path through the dense vines and creepers that blocked their way. Over time, their perseverance paid off as their hand-drawn maps began to reveal long-forgotten parts of the massive Mayan city of Caracol.

    But the more the pair found, the more they realized the extent of what remained uncovered. It would take several lifetimes, they figured, to reveal the true extent of Caracol.

    Then, in 2008, they got talking to a biologist colleague at the University of Central Florida where they worked. For years, he had been using airborne laser sensors known as Lidar (Light Detection And Ranging) to map and study forests and other vegetation. He suggested they give it a go.

    So, in 2009, the pair packed away their machetes and hiking boots and commissioned the National Center for Airborne Laser Mapping (NCALM) to fly a twin-engine plane backwards and forwards over the tree-tops firing pulses of laser light at the ground below. A few weeks later, the pair got their first look at the results.

    “I was completely astounded,” says Arlen Chase. “We had not expected the clarity that we saw in the imagery.”

    “I am pretty sure we uttered some expletives,” Diane adds politely.

    In less than a week, the team collected more data than they had in a quarter of century of hacking their way through the jungle. Analysis revealed a host of previously undiscovered features, including several in areas that they had previously mapped on foot. It was a revelation.

    Now, archaeologists around the world are beginning to embrace the same technique, flying aircraft over everything from Stonehenge to patches of scrub, in search of hidden treasures. The findings are already beginning to challenge conventional theories and change our view of the size and extent of ancient civilizations. But, while some say we are on the cusp of a new golden age of discovery, it is also beginning to throw up difficult questions about the disappearance of ancient civilizations.

    Using technology in archaeological expeditions is nothing new. Techniques similar to those used in the offshore oil industry have been used for years by archaeologists on the ground to spot buried structures. Increasingly, archaeologists are using satellite photography with success, for example, increasing the number of structures in the Nile valley including 17 new pyramids. In August, two more were found using images from Google Earth. Radar has even been used, famously uncovering vast new areas of the vast Cambodian temple complex Angkor Wat.

    But Lidar seems to offer several advantages. It is quick, relatively cheap and can be used to map large areas very quickly, particularly those covered in dense vegetation.

    The technology has been used in a variety of ways over the last two decades, from gauging distances between cars in adaptive cruise control to mapping forest canopies and detecting the amount of aerosols in the atmosphere. But, no matter what the use, most modern Lidar systems are essentially the same. All shoot thousands of pulses of laser light and then use sensors to detect any reflections. By measuring the time it takes between sending out a pulse and measuring the light bouncing back, software can begin to build up a picture of the machine’s surroundings. Using it in combination with GPS and other location technologies, it allows very accurate 3D maps to be built.

    Crucially, some of the laser light is also able to penetrate vegetation. So, in the case of areas covered in a forest canopy, such as in Caracol, some of the pulses will hit the top of tree canopy, some the middle, others the forest floor. Software can then be used to remove the points above the ground, according to University of Alabama archaeologist Dr Sarah Parcak, who is not part of the Chase team but has used Lidar at other sites. This leaves a detailed “digital elevation” model of the hidden forest floor with the ability to pick out features as small as 20cm across.

    “It is an amazing tool,” says Parcak. “You cannot use anything else in areas such as Central America to visualize Mayan ruins in a clear way.

    The measurements are exact enough that the Chases were able to overlay the new map onto the painstakingly, hand-created maps of their site with an unexpected level of exactitude. But what really astounded them was the amount of detail they had never seen before.

    Previously, they had mapped around 3.5 sq km of agricultural terraces on the site. The Lidar revealed more than 150 sq km more. In addition, it revealed thousands of new buildings arranged around squares, 11 new waterways, more than 60 caves as well as clues that suggest there could be up to 1400 water reservoirs on the site. All in all, one fly-over had radically increased the size of the ancient capital. Overnight it changed archaeologists’ perception of the site from a rarely-inhabited ceremonial center to a bustling city with a complex system of agriculture to support it.

    Devastating conclusion

    It is tempting put characterize this kind of revelation as a one-off success. But, Lidar’s success is not confined to Caracol. Further north, a team from Colorado State University has also used the technique in the Patzcuaro Basin, a region in the west of Mexico. The area was the centre of the Purepecha Empire – contemporaries of the Mayan and Aztec civilizations that have never caught public attention. They can be thought of as the people who stopped the advance of the Aztecs into San Diego and were also famous for their intricate metal work.

    In 2007, Colorado State University professor Chris Fisher began investigating the area. That year, he and his team found some impressive treasures including an imperial treasury building, where the leaders kept their stores of hummingbird and macaw feathers, the dominant currency. A year later, equipped with handheld GPS units his team spent three months on foot mapping the area in search of other treats. But, what they uncovered surprised even them.

    At a spot in an ancient road that previous surveys had marked down as little more than a widening of the carriageway, the team began to uncover evidence of buildings. Lots of buildings. Over three months, the team of between 12 and 16 people unearthed evidence for more than 1,400 buildings. It seemed that the wide spot in the road was in reality a surprisingly large pre-Hispanic capital.

    But it wasn’t until last year that Fisher and his team would know just how big. Equipped with Lidar the team flew over that spot recording 3,000 buildings in half the time it had taken them with ground surveys.

    “When Lidar was first used at Angamuco we had no idea how large the area was that included buildings and structures, if it was even a city,” team member Professor Steve Leisz told the BBC. Perhaps more surprisingly the team also found a ball court for a Meso American game called pok-ta-pok, and pyramids, including one that Fisher had walked within 10m of the previous year. “That was a complete surprise,” said Leisz.

    Finding new buildings and even cities is all very well and good - a new Machu Picchu or Chichen Itzas would be the crowning achievement of any archaeologists’ career. But, it goes without saying, most buildings and land modifications are rarely so dramatic. What is really important is who was in these buildings and how many. The more buildings, roads, wells, agricultural terraces and residential complexes are found, the higher the number of people that lived there.

    Population estimates of the Americas at the time of European contact have been steadily increasing over the past decades as archaeologists have slowly found new sites and dug over existing ones. That has gradually overturned the image of the Americas as a vast unexplored, unpopulated wilderness. But Lidar surveys are now beginning to dramatically change our view, says Fisher.

    “Widespread Lidar surveys will reveal a Mesoamerican landscape that was more densely settled, and an environment that was more pervasively modified, then previously thought,” said Fisher. Instead of a wilderness, here were two continents with vast populations, grand urban centres and widespread agriculture. But, perhaps more importantly, in revealing what life was like before the Conquistadors arrived in the 1500s, it also reveals the devastation that they wrought when they came into contact with native populations.

    “Before, a 40% die off seemed implausibly high,” said Fisher, “now 80% seems more likely.”

    ‘Exciting times’

    You may expect that dramatic findings and conclusions like this would mean the case for Lidar has been made. But not everyone is convinced by the laser revolution. Archaeologists like Rosemary Joyce, a professor of Mesoamerican archaeology at the University of California, Berkeley, and Russell Sheptak, a visiting scholar there, believe that the some of the proponent’s claims do not stack up.

    “What I specifically reject,” says Joyce, “is the claim that Lidar is both faster and cheaper than other archaeological methods, if we are interested in understanding sites, not just discovering them.”

    To really understand a site, you need boots on the ground, they say.

    These are arguments that the Lidar community are familiar with, and have some sympathy with. Both the Chases and Fisher teams admit that cruising over the tree-tops in a plane does not totally supplant the need to get up close and personal with a site. Without their 29 years of experience at Caracol, the Chases admit they would not have been able to recognize what they were seeing through Lidar as quickly as they did. Instead, it is a tool that allows them to quickly zoom in on potential features of interest. It also allows sites to be mapped quickly, allowing them to be preserved from looters and development.

    However, they take issue with arguments based on cost. Although they admit that Lidar can be expensive at face value – usually around $350 per square kilometer - they maintain it is still cheaper than traditional digs. For example, the Chases calculate the cost of Lidar per square kilometer is vanishingly small in comparison with the cost of travel, living on site, hiring workers, provisioning the dig and the thousand other misfortunes that an expedition to the jungle can encounter. Fisher, however, puts it more bluntly: “I don’t know how people can say it’s not cost-effective,” he says. “It saved us 10 years of research, for the cost of one season of excavation.”

    Over the next few years, as with all developments in computing, Fisher expects to see that cost continue to fall and its use to sky rocket. “Ten years from now, this is going to be like radiocarbon dating,” says Fisher, referring to a standard technique now used by all archaeologists to date finds. “Lidar is going to be folded into your research program, a really basic thing you do to understand the questions you want to answer.”

    Already, the teams have their eye on other areas where it could be used. For example, Arlen Chase believes it could help us to better understand settlement patterns along the Amazon, which can now only be glimpsed in satellite imagery on tree-cleared landscapes. He also believes it will also allow us to understand ancient African migrations and cultures, also currently obscured by forests. Other targets include Sri Lanka, India and other sites around South-East Asia. They also believe it could begin to be used to find sites such as ancient harbours, currently covered by water.

    “I suspect that, as we examine Lidar for different places, we’re going to wind up finding things in different places that we would not have thought to try to find,” says Leisz.

    Parcak puts it more prosaically. Technology, she says, is going to make us realize how little we know and how much left there is to explore.

    “It's the most exciting time in history to be an archaeologist,” she says.

    If you would like to comment on this article or anything else you have seen on Future, head over to our Facebook page or message us on Twitter.


    LiDar Technology Uncovers Ancient City Near Angkor Wat

    lidar image_980

    Angkor Wat and the surrounding area is an ancient 9th century Khmer construct of temples in Cambodia. LiDar is a 20th century invention that is probing secrets hidden deep within the surrounding jungle. LiDar (light detection and ranging), is an optical remote-sensing technique that transmits laser beams toward a target returning extremely accurate geospatial x,y,z measurements.

    Arial image of Angkor Wat, but LiDar reveals much more.

    Aerial surveys half a century ago used film cameras and slide rules. We’ve come a long way since then. The technology is discovering that there is more to Angkor Wat than meets the eye. The UNESCO site is an archaeologist’s dream in a country that thrived as part of an empire centuries ago and suffered through a civil war in our lifetime. Combined pieces of hardware turned dreams into reality. The major components of a LiDar system include a collection unit – possibly a land-based tripod or in the case at Angkor Wat, a helicopter – with an onboard computer and data storage devices. There is a laser scanner system, global positioning system (GPS), inertial measurement unit (IMU) and inertial navigation system (INS). The INS measures roll, pitch, and heading of the LiDar system. A light beam bounces back from the surface and a sensor records it to measure a range. When laser ranges are combined with position and orientation data generated from the GPS and IMU, scan angles, and calibration data, it results in a detailed, dense group of elevation points, called a point cloud.The shareable mass point cloud datasets can be managed, visualized, and analyzed. The point data becomes highly accurate geo-referenced x,y,z coordinates by analyzing the laser time range, laser scan angle, GPS position, and INS information.

    Each point in the point cloud has three-dimensional spatial coordinates – latitude, longitude, and height – that correspond to a particular point on the Earth’s surface from which the laser pulse was reflected.
    Topographic LiDar typically uses a near-infrared laser to map the land as at Angkor Wat, while bathymetric LiDar uses water-penetrating green light to also measure seafloor and riverbed elevations.

    Images carved into the temple proper and its walls hint of more discoveries waiting to be unearthed.

    LiDar provides archaeologists with the ability to create high-resolution digital elevation models of archaeological sites. The helicopter’s vantage point gives researchers access to areas difficult to reach on foot and can find secrets hidden beneath impenetrable forest canopies. The recent discoveries showed eerie outlines under the surrounding forest of temples never before seen by modern man. There are ceremonial boulevards which form a grid, dykes and man-made ponds which indicate large-scale hydraulic engineering typical of the Khmer empire which out of necessity had to concern itself with controlling the effects of frequent monsoons.

    French explorer, Henri Mouhot wrote in his journal in 1863 of the visible ruins he saw: “One of these temples, a rival to that of Solomon, and erected by some ancient Michelangelo, might take an honorable place beside our most beautiful buildings. It is grander than anything left to us by Greece or Rome.” No wonder modern explorers use every means possible to uncover more of the splendor. The BBC has much more on the topic including how they used LiDar.

    LiDar or 3D laser scanning originated in 1960 to detect submarines from aircraft. The science and its use have grown since then. Early in this century, Alex Lee, a then PhD Scholar at the School of Resources, Environment & Society in the Australian National University at Canberra was using LiDar in the Injune project for research involving biomass and global change science. It is his illustration you see below. This graphical representation is of the various elements of a small footprint airborne scanning laser system. Lee was looking at 1100 hectare of forest.

    Now, airborne LiDar sensors can capture existing conditions in true 3D. It is possible to model and analyze information virtually down to an individual tree in that forest. It can perform rapid surveys over large land areas with accuracy down to 5cm.
    LiDar permeates and facilitates measuring techniques utilized by several industries, including computer gaming, flood forecasting, meteorology, architecture, cellular network planning, and smart cars.

    Stanley, 2005 DARPA winner with LiDar on board

    Adaptive Cruise Control systems for automobiles have implemented this technology. LiDar units were used for short range detection on Stanley, the autonomous car that won the 2005 DARPA competition. Low-level modules fed raw data from LIDAR, the camera, GPS sets and inertial sensors into software programs that controlled the vehicle’s speed, direction and decision making.

    LiDar technology can also be put to use as an alternative to radar guns for speed limit tracking. Rather than relying on Doppler shifts to directly measure speed, policing LiDar uses the principle of time-of-flight to calculate speed.
    Physical objects can be captured by LiDar and re-created in the computer realm. When an object or scene has been made digital, it can be manipulated, colored, or textured into a detailed, accurate model. For gaming, it can be the basis for a replica of whole cities or the undulations of a race track.

    Angkor Wat isn’t the only game in town. Computer gamers benefit from LiDar, alongside archaeologists, architects, car manufacturers, and all varieties of scientists.
    The BBC provides a video in their interesting article. The BBC aired Jungle Atlantis already, but it can be seen October 5 in the US on The Smithsonian Channel under the name Angkor Revealed.


    LiDAR and the Archaeology Revolution

    There is no doubt that remote sensing technology has created a dramatic shift in the past few years concerning how scientists and researchers gather and analyze information about the Earth. Remote sensing, the use of satellites or aircraft to gather data about objects from a distance, has an almost infinite number of applications. This kind of technology has been used to monitor the environment, map the oceans, explore the Polar Regions, and much more. Now, a form of remote sensing technology called LiDAR is being used to lead a revolution in archaeology transforming how scientists understand human activity of the past.

    Changes in how archaeologists study the past are being brought about by advances in LiDAR technology. LiDAR, which stands for Light Detection and Ranging, is a method of remote sensing that uses light to measure varying distances to the Earth. This light is in the form of a pulsated laser, and these pulses can be used to produce exact data about the characteristics of Earth’s surface. LiDAR instruments are made up mainly of a laser, a special GPS receiver, and a scanner typically attached to an airplane or helicopter for use over a wide area.

    One of the places that LiDAR is having a significant impact in is the archaeological study of New England. Today, New England is heavily forested, which makes it extremely difficult for archaeologists to get a better understanding of how the region looked in colonial times. During the 1700s, New England was covered with roads, farm walls, and homesteads, but after they were largely abandoned in the 1950s, the forests grew back. Through the use of LiDAR, however, archaeologists are now able to uncover more of this ‘lost’ New England of subsistence farming, something many people have no idea existed.

    One of the principal researchers in this archaeology revolution of New England is Katharine Johnson from the University of Connecticut. Her research using LiDAR revealed a large amount of archaeological finds in both Connecticut and Massachusetts, areas that were critical for the earliest European settlers of North America. Johnson discovered sites that weren’t in any historical records, and with GPS coordinates from LiDAR, she says that she can walk into the woods and find building foundations or stone walls that no one imagined would be there. This shift in archaeology has been benefited by improvements in LiDAR technology with 1-meter (3.2 foot) resolutions now available.

    LiDAR reveals the underlying history of a landscape. Image from Kate Johnson.

    Beyond New England, the application of LiDAR in archaeology has been included other areas of the world. LiDAR has been used to help researchers uncover ancient Maya buildings, roads, and other features of this civilization and even create a three-dimensional map of a Maya settlement in Belize. LiDAR has also been employed in order to get high-resolution models of Renaissance palaces, like the Salone dei Cinquecento in Florence Italy. In England, LiDAR is being used to discover new sites in the plains of Stonehenge.


    Contents

    The modern name, Angkor Wat (Khmer: អង្គរវត្ត alternative name: នគរវត្ត ), [14] means "Temple City" or "City of Temples" in Khmer. Angkor ( អង្គរ ) meaning "city" or "capital city", is a vernacular form of the word nokor ( នគរ ), which comes from the Sanskrit/Pali word nagara (Devanāgarī: नगर). [15] Wat ( វត្ត ) is the Khmer word for "temple grounds", also derived from Sanskrit/Pali vāṭa (Devanāgarī: वाट), meaning "enclosure". [2]

    The original name of the temple was Vrah Viṣṇuloka or Parama Viṣṇuloka means god palce which comes from the Sanskrit/Pali , Vishnu one of the three supreme god in hindus , which was the posthumous name of its royal founder. [16] [10]

    Angkor Wat lies 5.5 kilometres (3.4 mi) north of the modern town of Siem Reap, and a short distance south and slightly east of the previous capital, which was centred at Baphuon. In an area of Cambodia where there is an essential group of ancient structures, it is the southernmost of Angkor's main sites. [ citation needed ]

    According to a myth, the construction of Angkor Wat was ordered by Indra to serve as a palace for his son Precha Ket Mealea. [17] According to the 13th-century Chinese traveller Zhou Daguan, some believed that the temple was constructed in a single night by a divine architect. [18]

    The initial design and construction of the temple took place in the first half of the 12th century, during the reign of Suryavarman II (ruled 1113 – c. 1150 ). Breaking from the Shaiva tradition of previous kings, Angkor Wat was instead dedicated to Vishnu. It was built as the king's state temple and capital city. As neither the foundation stela nor any contemporary inscriptions referring to the temple have been found, its original name is unknown, but it may have been known as "Varah Vishnu-lok" after the presiding deity. Work seems to have ended shortly after the king's death, leaving some of the bas-relief decoration unfinished. [19] The term Vrah Viṣṇuloka or Parama Viṣṇuloka literally means "The king who has gone to the supreme world of Vishnu", which refer to Suryavarman II posthumously and intend to venerate his glory and memory. [16]

    In 1177, approximately 27 years after the death of Suryavarman II, Angkor was sacked by the Chams, the traditional enemies of the Khmer. [20] Thereafter the empire was restored by a new king, Jayavarman VII, who established a new capital and state temple (Angkor Thom and the Bayon, respectively), a few kilometers north, dedicated to Buddhism, because the king believed that the Hindu gods had failed him. Angkor Wat was therefore also gradually converted into a Buddhist site, and many Hindu sculptures were replaced by Buddhist art. [21]

    Towards the end of the 12th century, Angkor Wat gradually transformed from a Hindu centre of worship to Buddhism, which continues to the present day. [9] Angkor Wat is unusual among the Angkor temples in that although it was largely neglected after the 16th century, it was never completely abandoned. [22] Fourteen inscriptions dated from the 17th century, discovered in the Angkor area, testify to Japanese Buddhist pilgrims that had established small settlements alongside Khmer locals. [23] At that time, the temple was thought by the Japanese visitors to be the famed Jetavana garden of the Buddha, which was originally located in the kingdom of Magadha, India. [24] The best-known inscription tells of Ukondayu Kazufusa, who celebrated the Khmer New Year at Angkor Wat in 1632. [25]

    One of the first Western visitors to the temple was António da Madalena, a Portuguese friar who visited in 1586 and said that it "is of such extraordinary construction that it is not possible to describe it with a pen, particularly since it is like no other building in the world. It has towers and decoration and all the refinements which the human genius can conceive of." [26]

    In 1860, the temple was effectively rediscovered by the French naturalist and explorer Henri Mouhot, who popularised the site in the West through the publication of travel notes, in which he wrote:

    One of these temples, a rival to that of Solomon, and erected by some ancient Michelangelo, might take an honorable place beside our most beautiful buildings. It is grander than anything left to us by Greece or Rome, and presents a sad contrast to the state of barbarism in which the nation is now plunged. [27]

    There were no ordinary dwellings or houses or other signs of settlement, including cooking utensils, weapons, or items of clothing usually found at ancient sites. Instead, there is only evidence of the monuments themselves. [28]

    The artistic legacy of Angkor Wat and other Khmer monuments in the Angkor region led directly to France adopting Cambodia as a protectorate on 11 August 1863 and invading Siam to take control of the ruins. This quickly led to Cambodia reclaiming lands in the northwestern corner of the country that had been under Siamese (Thai) control since AD 1351 (Manich Jumsai 2001), or by some accounts, AD 1431. [29]

    Angkor Wat's aesthetics were on display in the plaster cast museum of Louis Delaporte called musée Indo-chinois which existed in the Parisian Trocadero Palace from c.1880 to the mid-1920s. [30]

    The 20th century saw a considerable restoration of Angkor Wat. [31] Gradually teams of laborers and archeologists pushed back the jungle and exposed the expanses of stone, permitting the sun to once again illuminate the dark corners of the temple. Angkor Wat caught the attention and imagination of a wider audience in Europe when the pavilion of French protectorate of Cambodia, as part of French Indochina, recreated the life-size replica of Angkor Wat during Paris Colonial Exposition in 1931. [32]

    Cambodia gained independence from France on 9 November 1953 and has controlled Angkor Wat since that time. It is safe to say that from the colonial period onwards until the site's nomination as UNESCO World Heritage in 1992, this specific temple of Angkor Wat was instrumental in the formation of the modern and gradually globalised concept of built cultural heritage. [33]

    Restoration work was interrupted by the Cambodian Civil War and Khmer Rouge control of the country during the 1970s and 1980s, but relatively little damage was done during this period. Camping Khmer Rouge forces used whatever wood remained in the building structures for firewood, and a shoot-out between Khmer Rouge and Vietnamese forces put a few bullet holes in a bas relief. Far more damage was done after the wars, by art thieves working out of Thailand, which, in the late 1980s and early 1990s, claimed almost every head that could be lopped off the structures, including reconstructions. [34]

    The temple is a powerful symbol of Cambodia, and is a source of great national pride that has factored into Cambodia's diplomatic relations with France, the United States, and its neighbour Thailand. A depiction of Angkor Wat has been a part of Cambodian national flags since the introduction of the first version circa 1863. [35] From a larger historical and even transcultural perspective, however, the temple of Angkor Wat did not become a symbol of national pride sui generis but had been inscribed into a larger politico-cultural process of French-colonial heritage production in which the original temple site was presented in French colonial and universal exhibitions in Paris and Marseille between 1889 and 1937. [36]

    In December 2015, it was announced that a research team from University of Sydney had found a previously unseen ensemble of buried towers built and demolished during the construction of Angkor Wat, as well as a massive structure of unknown purpose on its south side and wooden fortifications. The findings also include evidence of low-density residential occupation in the region, with a road grid, ponds, and mounds. These indicate that the temple precinct, bounded by moat and wall, may not have been used exclusively by the priestly elite, as was previously thought. The team used LiDAR, ground-penetrating radar and targeted excavation to map Angkor Wat. [37]

    Site and plan Edit

    Angkor Wat is a unique combination of the temple mountain (the standard design for the empire's state temples) and the later plan of concentric galleries. The construction of Angkor Wat also suggests that there was a celestial significance with certain features of the temple. This is observed in the temple's east–west orientation, and lines of sight from terraces within the temple that show specific towers to be at the precise location of the sunrise on a solstice. [38] The temple is a representation of Mount Meru, the home of the gods: the central quincunx of towers symbolises the five peaks of the mountain, and the walls and moat symbolize the surrounding mountain ranges and ocean. [39] Access to the upper areas of the temple was progressively more exclusive, with the laity being admitted only to the lowest level. [40]

    The Angkor Wat temple's main tower aligns to the morning sun of the spring equinox. [41] [42] Unlike most Khmer temples, Angkor Wat is oriented to the west rather than the east. This has led many (including Maurice Glaize and George Coedès) to conclude that Suryavarman intended it to serve as his funerary temple. [43] [44] Further evidence for this view is provided by the bas-reliefs, which proceed in a counter-clockwise direction—prasavya in Hindu terminology—as this is the reverse of the normal order. Rituals take place in reverse order during Brahminic funeral services. [31] The archaeologist Charles Higham also describes a container which may have been a funerary jar which was recovered from the central tower. [45] It has been nominated by some as the greatest expenditure of energy on the disposal of a corpse. [46] Freeman and Jacques, however, note that several other temples of Angkor depart from the typical eastern orientation, and suggest that Angkor Wat's alignment was due to its dedication to Vishnu, who was associated with the west. [39]

    Drawing on the temple's alignment and dimensions, and on the content and arrangement of the bas-reliefs, researcher Eleanor Mannikka argues that the structure represents a claimed new era of peace under King Suryavarman II: "as the measurements of solar and lunar time cycles were built into the sacred space of Angkor Wat, this divine mandate to rule was anchored to consecrated chambers and corridors meant to perpetuate the king's power and to honour and placate the deities manifest in the heavens above." [47] [48] Mannikka's suggestions have been received with a mixture of interest and scepticism in academic circles. [45] She distances herself from the speculations of others, such as Graham Hancock, that Angkor Wat is part of a representation of the constellation Draco. [49]

    Style Edit

    Angkor Wat is the prime example of the classical style of Khmer architecture—the Angkor Wat style—to which it has given its name. By the 12th century Khmer architects had become skilled and confident in the use of sandstone (rather than brick or laterite) as the main building material. Most of the visible areas are of sandstone blocks, while laterite was used for the outer wall and for hidden structural parts. The binding agent used to join the blocks is yet to be identified, although natural resins or slaked lime has been suggested. [50]

    The temple has drawn praise above all for the harmony of its design. According to Maurice Glaize, a mid-20th-century conservator of Angkor, the temple "attains a classic perfection by the restrained monumentality of its finely balanced elements and the precise arrangement of its proportions. It is a work of power, unity, and style." [51]

    Architecturally, the elements characteristic of the style include: the ogival, redented towers shaped like lotus buds half-galleries to broaden passageways axial galleries connecting enclosures and the cruciform terraces which appear along the main axis of the temple. Typical decorative elements are devatas (or apsaras), bas-reliefs, and on pediments extensive garlands and narrative scenes. The statuary of Angkor Wat is considered conservative, being more static and less graceful than earlier work. [52] Other elements of the design have been destroyed by looting and the passage of time, including gilded stucco on the towers, gilding on some figures on the bas-reliefs, and wooden ceiling panels and doors. [53]

    Features Edit

    Outer enclosure Edit

    The outer wall, 1,024 m (3,360 ft) by 802 m (2,631 ft) and 4.5 m (15 ft) high, is surrounded by a 30 m (98 ft) apron of open ground and a moat 190 m (620 ft) wide and over 5 kilometres (3 mi) in perimeter. [6] The moat extends 1.5 kilometres from east to west and 1.3 kilometres from north to south. [55] Access to the temple is by an earth bank to the east and a sandstone causeway to the west the latter, the main entrance, is a later addition, possibly replacing a wooden bridge. [56] There are gopuras at each of the cardinal points the western is by far the largest and has three ruined towers. Glaize notes that this gopura both hides and echoes the form of the temple proper. [57] Under the southern tower is a statue known as Ta Reach, originally an eight-armed statue of Vishnu may have occupied the temple's central shrine. [56] Galleries run between the towers and as far as two further entrances on either side of the gopura often referred to as "elephant gates", as they are large enough to admit those animals. These galleries have square pillars on the outer (west) side and a closed wall on the inner (east) side. The ceiling between the pillars is decorated with lotus rosettes the west face of the wall with dancing figures and the east face of the wall with balustered windows, dancing male figures on prancing animals, and devatas, including (south of the entrance) the only one in the temple to be showing her teeth.

    The outer wall encloses a space of 820,000 square metres (203 acres), which besides the temple proper was originally occupied by the city and, to the north of the temple, the royal palace. Like all secular buildings of Angkor, these were built of perishable materials rather than of stone, so nothing remains of them except the outlines of some of the streets. [58] Most of the area is now covered by forest. A 350 m (1,150 ft) causeway connects the western gopura to the temple proper, with naga balustrades and six sets of steps leading down to the city on either side. Each side also features a library with entrances at each cardinal point, in front of the third set of stairs from the entrance, and a pond between the library and the temple itself. The ponds are later additions to the design, as is the cruciform terrace guarded by lions connecting the causeway to the central structure. [58]

    Central structure Edit

    The temple stands on a terrace raised higher than the city. It is made of three rectangular galleries rising to a central tower, each level higher than the last. The two inner galleries each have four large towers at their ordinal​ corners (that is, NW, NE, SE and SW) surrounding a higher fifth tower. This pattern is sometimes called a quincunx and represents the mountains of Meru. Because the temple faces west, the features are all set back towards the east, leaving more space to be filled in each enclosure and gallery on the west side for the same reason the west-facing steps are shallower than those on the other sides.

    Mannikka interprets the galleries as being dedicated to the king, Brahma, the moon, and Vishnu. [19] Each gallery has a gopura at each of the points. The outer gallery measures 187 m (614 ft) by 215 m (705 ft), with pavilions rather than towers at the corners. The gallery is open to the outside of the temple, with columned half-galleries extending and buttressing the structure. Connecting the outer gallery to the second enclosure on the west side is a cruciform cloister called Preah Poan (meaning "The Thousand Buddhas" Gallery). [10] Buddha images were left in the cloister by pilgrims over the centuries, although most have now been removed. This area has many inscriptions relating the good deeds of pilgrims, most written in Khmer but others in Burmese and Japanese. The four small courtyards marked out by the cloister may originally have been filled with water. [59] North and south of the cloister are libraries.

    Beyond, the second and inner galleries are connected to each other and to two flanking libraries by another cruciform terrace, again a later addition. From the second level upwards, devatas abound on the walls, singly or in groups of up to four. The second-level enclosure is 100 m (330 ft) by 115 m (377 ft), and may originally have been flooded to represent the ocean around Mount Meru. [60] Three sets of steps on each side lead up to the corner towers and gopuras of the inner gallery. The very steep stairways represent the difficulty of ascending to the kingdom of the gods. [61] This inner gallery, called the Bakan, is a 60 m (200 ft) square with axial galleries connecting each gopura with the central shrine, and subsidiary shrines located below the corner towers.

    The roofings of the galleries are decorated with the motif of the body of a snake ending in the heads of lions or garudas. Carved lintels and pediments decorate the entrances to the galleries and to the shrines. The tower above the central shrine rises 43 m (141 ft) to a height of 65 m (213 ft) above the ground unlike those of previous temple mountains, the central tower is raised above the surrounding four. [5] The shrine itself, originally occupied by a statue of Vishnu and open on each side, was walled in when the temple was converted to Theravada Buddhism, the new walls featuring standing Buddhas. In 1934, the conservator George Trouvé excavated the pit beneath the central shrine: filled with sand and water it had already been robbed of its treasure, but he did find a sacred foundation deposit of gold leaf two metres above ground level. [62]

    Decoration Edit

    Integrated with the architecture of the building, and one of the causes for its fame is Angkor Wat's extensive decoration, which predominantly takes the form of bas-relief friezes. The inner walls of the outer gallery bear a series of large-scale scenes mainly depicting episodes from the Hindu epics the Ramayana and the Mahabharata. Higham has called these "the greatest known linear arrangement of stone carving". [63] From the north-west corner anti-clockwise, the western gallery shows the Battle of Lanka (from the Ramayana, in which Rama defeats Ravana) and the Battle of Kurukshetra (from the Mahabharata, showing the mutual annihilation of the Kaurava and Pandava clans). On the southern gallery follow the only historical scene, a procession of Suryavarman II, then the 32 hells and 37 heavens of Hinduism. [64]


    New NASA laser technology reveals how ice measures up

    NASA's Multiple Altimeter Beam Experimental Lidar flew over Southwest Greenland's glaciers and sea ice to test a new method of measuring the height of Earth from space. Image Credit: NASA/Tim Williams

    When a high-altitude aircraft flew over the icy Arctic Ocean and the snow-covered terrain of Greenland in April 2012, it was the first polar test of a new laser-based technology to measure the height of Earth from space.

    Aboard that aircraft flew the Multiple Altimeter Beam Experimental Lidar, or MABEL, which is an airborne test bed instrument for NASA's ICESat-2 satellite mission slated to launch in 2017. Both MABEL and ICESat-2's ATLAS instrument are photon counters &ndash they send out pulses of green laser light and time how long it takes individual light photons to bounce off Earth's surface and return. That time, along with ATLAS&rsquo exact position from an onboard GPS, will be plugged into computer programs to tell researchers the elevation of Earth's surface &ndash measuring change to as little as the width of a pencil.

    This kind of photon-counting technology is novel for satellites from 2003 to 2009, ICESat-1&rsquos instrument looked at the intensity of a returned laser signal, which included many photons. So getting individual photon data from MABEL helps scientists prepare for the vast amounts of elevation data they'll get from ICESat-2.

    MABEL, short for "Multiple Altimeter Beam Experimental Lidar," serves as an ICESat-2 simulator. Image Credit: NASA/Kelly Brunt

    ICESat-2 is tasked with measuring elevation across Earth's entire surface, including vegetation and oceans, but with a focus on change in the frozen areas of the planet, where scientists have observed dramatic impacts from climate change. There, two types of ice &ndash ice sheets and sea ice &ndash reflect light photons in different patterns. Ice sheets and glaciers are found on land, like Greenland and Antarctica, and are formed as frozen snow and rain accumulates. Sea ice, on the other hand, is frozen seawater, found floating in the Arctic Ocean and offshore of Antarctica.

    MABEL's 2012 Greenland campaign was designed to observe a range of interesting icy features, said Bill Cook, MABEL's lead scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. With the photon counts from different surfaces, other scientists could start analyzing the data to determine which methods of analyzing the data allow them to best measure the elevation of Earth's surface.

    "We wanted to get a wide variety of target types, so that the science team would have a lot of data to develop algorithms," Cook said. "This was our first real dedicated science mission."

    The flights over the ocean near Greenland, for example, allowed researchers to demonstrate that they can measure the height difference between open water and sea ice, which is key to determining the ice thickness. MABEL can detect enough of the laser light photons that bounce off Earth surface and return to the instrument, and programs can then make necessary elevation calculations, Cook said.

    "Part of what we're doing with MABEL is to demonstrate ICESat-2's instrument is going to have the right sensitivity to do the measurements," Cook said. "You can do this photon counting if you have enough photons."

    In an article recently published in the Journal of Atmospheric and Oceanic Technology, Kwok and his colleagues showed how to calculate elevation from MABEL data, and do so over different types of ice &ndash from open water, to thin, glassy ice, to the snow-covered ice.

    "We were pretty happy with the precision," Kwok said. "The flat areas are flat to centimeter level, and the rough areas are rough." And the density of photons detection could also tell researchers what type of ice the instrument was flying over.

    The contours of the icy surface are also important when monitoring ice sheets and glaciers covering land. The original ICESat-1 mission employed a single laser, which made it more difficult to measure whether the ice sheet had gained or lost elevation. With a single beam, when the instrument flew over a spot a second time, researchers couldn't tell if the snowpack had melted or if the laser was slightly off and pointed down a hill. Because of this, scientists needed 10 passes over an area to determine whether the ice sheet was changing, said Kelly Brunt, a research scientist at NASA Goddard.

    "ICESat-1 was fantastic, but it was a single beam instrument," Brunt said. "We're more interested in repeating tracks to monitor change &ndash that's hard to do."

    ICESat-2 addresses this problem by splitting the laser into six beams. These are arranged in three pairs, and the beams within a pair are spaced 295 feet (90 meters), or just less than a football field apart. By comparing the height of one site to the height of its neighbor, scientists can determine the terrain's general slope.

    Brunt and her colleagues used MABEL data from the 2012 Greenland campaign to try to detect slopes as shallow as 4 percent incline their results will be published in the May 2014 issue of the journal Geoscience and Remote Sensing Letters. They counted only a portion of the photons, in order to simulate the weaker laser beams that ICESat-2 will carry. With computer programs to determine the slope, the researchers verified it against results from earlier missions.

    "The precision is great," Brunt said. "We're very confident that with ICESat-2's beam pair, we can see slope."

    And there are still more things for MABEL to measure. The instrument team is planning a 2014 summer campaign to fly over glaciers and ice sheets in warmer weather. "We want to see what the effects of the melt is," Cook said. "How do glaciers look if they're warmer, rather than colder?"


    Watch the video: Συνέντευξη οδηγού καρτ που καταπλάκωσε τον 6άχρονο στην Πάτρα: Τι πήγε στραβά? (July 2022).


    Comments:

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    3. Kegrel

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    4. Makya

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