Preserving Romania’s speleological heritage with point cloud and GNSS data

Author: George Damian, Renata Barradas

3 d激光扫描提供了一种高分辨率、非invasive documentation method to understand natural and cultural sites and manage its exposure to natural and man-made threats. Researchers in diverse fields are unlocking numerous applications using this technology, just like speleologists who are using laser scan data to study and measure caves with millimetre-level accuracy in a non-intrusive way. Point cloud data allows experts to extract cartographic information and calculate areas and volumes to study the evolution of topographic and bathymetric features in caves.

To preserve and understand Romania’s speleological heritage,Top Geocart, the Leica Geosystems’ dealer in Romania, laser scanned the Meziad Cave, a 6,298-metre natural wonder in the western Carpathians. The Meziad Cave, the first cave adapted for tourism in Romania, is known for its spectacular subterranean landscapes with beautiful speleothems (stalactites, stalagmites, columns and curtains). The cave is also home to one of the largest colony of bats in South-East Europe and microscopic endemic organisms (some of them confined to the Meziad Cave).

这项高分辨率3D文档旨在准确捕获该地点的复杂性，并引入积极的保护措施，以维护或恢复现场，然后进行任何考古学和古生物学侵入性研究，以修改原始地点。此外，顶级Geocart创建了3D模型和其他可交付成果，以使其客户Spelemat能够存储，组织和检索信息以进行进一步分析。数据提供了文件并记录了这种自然和文化遗产的原位状态。

A mission inside the cave

顶级Geocart与Spelemat的专家一起设计了该项目，并计划在地球内部进行此任务。理解，尊重和促进技术和地理空间数据的使用的这组专家，他们收集了现场数据，而不会影响环境。除了使用非侵入/非侵入性技术外，该团队还必须考虑正确的时机才能进入洞穴，因为天气和洞穴的河流流是成功完成此任务的关键因素。

Specialists from Top Geocart used best-in-class software and hardware, including:

• The Leica RTC360 3D laser scanner
• Leica BLK360成像激光扫描仪
• The Leica Viva GS16 GNSS smart antenna
• The Leica GS18 T RTK GNSS rover
• Leica Disto™S910

对于点云对齐，建模和GNSS网络团队依赖：

• Leica Infinity software
• Leica Cyclone寄存器3603D laser scanning point cloud registration software
• Leica Cyclone模型
• Leica Cyclone 3dr
• Leica GNSS Spider software

The team scouted the mountain area and geo-referenced it with the GS16 and GS18 T GNSS RTK rovers with real-time corrections from the Romanian National Reference Stations Network (ROMPOS), running on GNSS Spider software. SmartLink corrections were necessary since the mountainous environment with slopes and trees obstructed the area and from time to time GSM/GPRS signal was lost. The capability of GS16 and GS18 T to use the SmartLink Service was key to cover these gaps and always have a precise position. To deliver the most accurate positions, the team also relied on the Leica RTKplus technology in both RTK rovers as it intelligently adapts to changing conditions by selecting the optimal GNSS signals.

在洞穴的内部，团队带着特殊的衣服和配件穿过河水，以安全地运输设备。在防水容器和漂浮袋的内部，RTC360和BLK360从位置漂移到位置。速度和精度是原始的，同时在10°C度以下的温度下，在胸部上方的水位上扫描。

Geared with the RTC360, the team captured the larger parts of the cave and artefacts, creating coloured 3D point clouds in under two minutes. With a scanning speed of up to 2 million points per second, advanced HDR imaging system and automated target-less field registration in the RTC360, Top Geocart captured the sites of interest inside the cave in two hours at 750 meters per hour.

At the push of a button, Top Geocart captured full-colour panoramic images overlaid on a high-accuracy point cloud for the narrow parts of the cave with the smallest and lightest imaging laser scanner - the BLK360. For those areas where it was not possible to set on a tripod the laser scanners, measurements were made with the DISTO™ 910.

The mission’s deliverables

Outside of the cave close to the entry, the team automatically and seamlessly transferred data from site to office using Leica Exchange, the exchange service provided by Leica Geosystems, reducing time in the inhospitable environment. Transferring the data easily between the field and the office with Leica Exchange allowed experts to perform a first check of the data onsite with Leica DISTO™ Transfer and Leica DISTO™ Plan App. UsingLeica Cyclone Field 360顶部的地理器在洞穴入口自动预注册和对齐扫描。

Back in the office, point cloud data from the BLK360 and RTC360 was registered with Cyclone REGISTER 360. The GNSS data was checked and processed with Infinity software, in the GNSS project were imported the DISTO™ data, too. Together with Spelemat, Top Geocart created a unified point cloud, as Cyclone REGISTER 360 project, and exported in E57 and LGS formats to visualise it withJetStream Viewer，一种轻重点云查看工具。E57文件是在Leica Cyclone 3DR中导入的，以从点云中创建网格和计算数字地形模型（DTM）。

Experts also created 2D topographical maps and 3D DTM with data from the GS16 and GS18 T RTK rovers to develop new tracks and paths for visitors. Distances and CAD files with 3D points and pictures were extracted from the data collected with the DISTO™ S910.

The data provided will support researchers, tourists and facility managers alike. It will guide feasibility studies for touristic plans and be used as marketing material to invite visitors to explore this natural wonder. Point cloud deliverables provide researchers with a digital twin of the cave where they can extract any profile and 3D measurement. At the same time, GNSS data helped to identify the areas and paths to create access for tourists and scientists.

“Leica Geosystems and Top Geocart provide complete software and hardware set for the entire workflow. The sensors have the capabilities to work in difficult environments and meet the highest standards in measurement excellence. The management and specialists fromSpelemat承认他们能够比以往任何时候Spelemat的洞穴管理专家Viorel Lascu说。

The success of capturing the Meziad Cave convinced Spelemat to invest in RTC360, BLK360, DISTO™ to keep exploring and understanding Romania’s natural wonders.