Preserving Romania’s Speleological Heritage with point cloud and GNSS Data

Author: George Damian, Renata Barradas

3D激光扫描提供了一种高分辨率的非侵入性文档方法，可以理解自然和文化遗址，并管理其自然和人造威胁的暴露。不同领域的研究人员正在使用该技术解锁众多应用，就像使用激光扫描数据以毫米级别准确性研究和测量洞穴的Speleologist，以非侵入性的方式进行测量。点云数据允许专家提取制图信息并计算区域和卷，以研究洞穴中地形和测深特征的演变。

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).

This high-resolution 3D documentation aimed to accurately capture the site’s complexity and to introduce positive conservation measures to maintain or restore the site before conducting any archaeological and palaeontological invasive research that can modify the original site. Moreover, Top Geocart created 3D models and other deliverables to enable its customer, Spelemat, to store, organise and retrieve information for further analysis. The data provided documents and records the in-situ state of this natural and cultural heritage.

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。

顶级Geocart的专家使用了一流的软件和硬件，包括：

• Leica RTC360 3D激光扫描仪
• 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 MODEL
• 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.

In the interior of the cave, the team moved through the river’s water with special clothes and accessories to safely transport the equipment. Inside of the waterproof containers and floating bags, the RTC360 and BLK360 drifted from location to location. Speed and precision are primordial while scanning with a water level above your chest in temperatures below 10 °C degrees.

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

在靠近条目的洞穴之外，团队使用Leica Geosystems提供的Exchange Service自动并无缝将数据从站点转移到办公室，从而减少了在荒凉环境中的时间。通过Leica Exchange轻松在现场和办公室之间传输数据，使专家可以使用Leica Disto™Transfer和Leica Disto™Plan应用程序对数据进行首次检查。使用Leica Cyclone Field 360顶部的地理器在洞穴入口自动预注册和对齐扫描。

回到办公室，BLK360和RTC360的点云数据已在Cyclone寄存器360中注册。GNSS数据被检查并使用Infinity软件处理，在GNSS项目中也导入了Disto™数据。与Spelemat一起，Top Geocart创建了一个统一的点云，作为Cyclone寄存器360项目，并以E57和LGS格式导出，以使用JetStream 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.

提供的数据将支持研究人员,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和Top Geocart为整个工作流提供完整的软件和硬件集。传感器具有在困难环境中工作的功能，并在卓越的测量中达到最高标准。来自Spelemat承认他们能够比以往任何时候Spelemat的洞穴管理专家Viorel Lascu说。

捕获Meziad Cave的成功说服了Spelemat投资RTC360，BLK360，Disto™，以继续探索和理解罗马尼亚的自然奇观。