Pulling artifacts from the jungle using Full Waveform LiDAR

Author:Penny Boviatsou

高棉帝国的伟大及其作为柬埔寨文化遗产的一部分的重要性刚刚开始展开。有史以来在考古项目上开展的最广泛的空降激光扫描运动揭示了埋葬在柬埔寨丛林中的古老城市。

Lidar被证明是更好地了解我们历史的催化剂。创新技术正在改变考古学，并迅速成为考古学家的强大工具。激光可以穿透上覆的植被，并且覆盖地面的速度比步行得多的速度要快。

The Angkor complex is one of the most important archaeological 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.

隐藏但没有忘记

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:

• The Khmer Archaeology LiDAR Consortium (KALC) in April 2012 and the
• 柬埔寨考古LiDar倡议（CALI）于2015年4月决定扩展到高棉历史和考古学的传统方法之外的观点。

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.

The premise for the projects was that LiDAR could provide key information hiding under tree canopy, needed to fully assess the extent and impact of the Khmer civilisation in Southeast Asia, particularly in Cambodia. To accomplish the goals, several meetings tool place between Francisco Goncalves, Professor Roland Fletcher and Dr. Damian Evans. These allowed PTMI to understand the landscape and vegetation challenges, site visits were also planned prior to acquisition.

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.

The first findings came in 2012 when the company worked closely with Dr. Damian Evans and the Consortium’s associates. By flying a helicopter mounted with a POD carrying, a Leica LiDAR scanner equipped with waveform data capture and a Leica digital aerial camera, PTMI gathered data that confirmed the existence of Mahedraparvata, an ancient temple city whose existence had been known for decades.

最近分析的数据，于2015年捕获考古项目有史以来最广泛的空降研究, 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 generated maps revealed multiple medieval cities hidden on the forest floor and upended what we knew about the lived-in spaces around Angkor and other temple complexes across Cambodia,” said Dr Damian Evans. “The vegetation was obscuring these monumental sites. The LiDAR technology allowed us to see through the vegetation.”

Unveiling the secrets of an empire

In 2015, PTMI covered 1600 square km with the goal to deliver the Cambodia Archaeology LiDAR Initiative, the finest and most complete data coverage of their areas of interest, and provide an opening for future archaeology LiDAR investigation. At the planning stages of the project, PTMI spent approximately a year discussing approaches to the LiDAR and Digital Air Photo (DAP) acquisition.

弗朗西斯科·冈萨（FranciscoGonçalves）和克里斯·克罗马蒂（Chris Chromarty）步行了计划进行激光雷达和DAP采购的区域，并研究了树木覆盖下的地形和植被，以及激光雷达可能检测到的考古特征的类型。

“考古学使我着迷”says Francisco Gonçalves, President Director at PTMI.“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 used Leica Geosystems’s LiDAR mapping systems to scan the Cambodian jungle. The company collected data with LiDAR technology that penetrated the dense Cambodian forests and thick vegetation, gathering information about the soil’s surface and terrain elevation that enabled archaeologists to find traces of extensive networks around Angkor. Digital aerial photography was simultaneously collected with the LiDAR data.

"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."

所有LIDAR数据均使用安装在柬埔寨的AS350 B2直升机（Helistar）中的POD获取，然后使用配备配备DataPort可移动驱动器的处理站进行了调整和处理，PTMI调整和处理处理中心。PTMI计划了数据采集，调整了空气图像，并将激光雷达分为地面和非地点。所有结果都交付给了卡利，埃文斯和他的团队能够准备考古分析。

LIDAR - 考古学的新工具

激光雷达（LiDar）渗透茂密的植被的能力意味着自居住期以来，寺庙综合体和周边地区能够清楚地看到。有了激光雷达的地图，细微的地形变化已取消了道路网络，占领土墩和其他城市规划标志，这些标志即使从地面也无法检测到。

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.

考古领域的研究人员认为，这些是近年来最重要的考古发现。