使用全波形激光雷达从丛林中拉出伪影

作者：Penny Boviatsou

The greatness of Khmer Empire as well as its importance as part of the Cambodian cultural heritage is just beginning to unfold. The most extensive airborne laser scanning campaign ever conducted on an archaeological project revealed a massive complex of ancient cities buried in the Cambodian jungle.

LiDAR is proving to be a catalyst for a better understanding of our history. The innovative technology is transforming archaeology and is fast becoming a powerful tool for archaeologists; the lasers can penetrate overlying vegetation and cover swaths of ground extremely faster than they could be studied on foot.

吴哥是一个复杂的最重要的基于“增大化现实”技术chaeological sites in Siem Reap in Southeast Asia and the Angkor Wat one of the world’s most recognisable temples. In the late 12th and early 13th centuries the city was at its peak with historians describing an urban centre extending over nearly 1036 square km. Angkor was the centre of a once massive and powerful nation believed to be the largest in the world at the time, with up to 1 million inhabitants.

Hidden but not forgotten

Nothing ignites a researcher’s imagination like the prospect of a lost metropolis. Archaeologists in Cambodia after numerous years of research have recently announced the discovery of multiple medieval cities hidden beneath the tropical forest floor near Angkor and other archaeological sites across the Kingdom of Cambodia. The colossal discovery challenges the theories that the Angkorian people eventually abandoned the cities for ones in the South as it was until recently believed. The archaeologists were able to discover the ruins of the lost civilisation thanks to airborne laser scanning technology:

• 高棉考古激光雷达联盟（KALC）于2012年4月和
• Cambodia Archaeology LiDAR Initiative (CALI) in April 2015 decided to widen the perspective beyond conventional methods to Khmer history and archaeology.

Both projects were designed by Francisco Gonçalves and Chris Cromarty from PT Map Tiga Internasional (PTMI - formerly PT. McElhanney Indonesia), a Jakarta-based company providing aerial mapping and surveying expertise.

这些项目的前提是，LiDar可以提供隐藏在树冠下的关键信息，以充分评估高棉文明在东南亚，特别是在柬埔寨的程度和影响。为了实现目标，弗朗西斯科·冈卡维斯（Francisco Goncalves），罗兰·弗莱彻（Roland Fletcher）教授和达米安·埃文斯（Damian Evans）博士之间的几个会议工具位置。这些使PTMI了解景观和植被挑战，在收购之前还计划了现场访问。

PTMI acquired Leica Geosystems’s LiDAR and digital aerial photography sensors to provide the researchers with high resolution aerial imagery as well as high density ground LiDAR points to the archaeologists while scanning the Cambodian jungle.

第一个发现是在2012年与达米安·埃文斯（Damian Evans）和财团的同事密切合作的2012年。通过驾驶装有吊舱的直升机，配备了波形数据捕获的Leica Lidar扫描仪和一台Leica Digital Perialial摄像头，PTMI收集了数据，证实了Mahedraparvata的存在，Mahedraparvata是一座古老的寺庙城市，其存在已有数十年了。

The recently analysed data, captured in 2015 duringthe most extensive airborne study ever undertaken by an archaeological project, uncovered the total scale of the Khmer Empire’s urban extent and found the temple complexes to be extremely greater than was previously believed.

“LIDAR产生的地图揭示了隐藏在森林地板上的多个中世纪城市，并颠覆了我们对吴哥四周围的居住空间和柬埔寨其他寺庙建筑群的了解达米安·埃文斯博士说。“植被掩盖了这些巨大的地点。激光雷达技术使我们能够看到植被.”

Unveiling the secrets of an empire

2015年，PTMI覆盖了1600平方公里，目的是提供柬埔寨考古LIDAR倡议，这是其感兴趣领域最好，最完整的数据覆盖率，并为未来的考古激光雷达调查提供开放。在该项目的计划阶段，PTMI花了大约一年的时间讨论了激光雷达和数字空气照片（DAP）的方法。

Francisco Gonçalves and Chris Chromarty walked areas planned for LiDAR and DAP acquisition, and studied the terrain and vegetation under tree cover and the type of archaeological features the LiDAR could detect.

“Archaeology fascinates me,”PTMI总裁FranciscoGonçalves说。“What secrets are hidden, where our ancestors did built cities and why they abandoned them. Penetrating the Cambodian jungle with the Leica Geosystems technology we were able to acquire LiDAR point data that precisely revealed not only the structure of the land scape but also constructions, roads, canals, structural foundations and agricultural terraces.”

PTMI使用Leica Geosystems的LiDAR映射系统来扫描柬埔寨丛林。该公司使用LiDAR技术收集了数据，这些技术渗透到茂密的柬埔寨森林和茂密的植被，收集有关土壤表面和地形高程的信息，使考古学家能够在吴哥附近找到广泛的网络痕迹。数码航空摄影与LIDAR数据同时收集。

"Agricultural fields and other structures have remained hidden by growing trees for centuries, but LiDAR technology is changing the way we view the world," said Professor Roland Fletcher. "Cases of recently deforested lands challenge the theories that ancient forests are 'pristine ecosystems', people shaped the landscapes where forests are located for thousands of years."

All LiDAR data was acquired using a POD mounted in an AS350 B2 helicopter (HeliStar) based in Cambodia and then adjusted and processed by PTMI using processing workstations equipped with DataPort removable drive carriers, allowing easy movement of the large data files from the aircraft to the processing centre. PTMI planned the data acquisition, adjusted the air imagery and classified the LiDAR into ground and non-ground points. All the results were delivered to CALI where Evans and his team were able to prepare the archaeological analysis.

LiDAR – a new tool for archaeological prospection

LiDAR’s ability to penetrate dense vegetation has meant that the temple complexes and surrounding areas are able to be seen clearly for the first time since the habitation period. With LiDAR-generated maps, subtle topographical changes have traced out road networks, occupation mounds and other urban planning signs that were previously undetectable even from the ground.

The LiDAR-made maps enable the CALI researchers to make more targeted excursions at the site whilst the LiDAR data determine the locations where further research might be useful.

Researchers in the archaeological sphere agree these are the most significant archaeological discoveries in recent years.