使用3D激光扫描来检测盐和冰洞的结构变化

作者：Tommaso Santagata

陆地激光扫描（TLS）已用于地下调查已有十多年了，并且越来越多地用于洞穴的A勘探和研究中。虚拟地理机构的Tommaso SantagataVigea最近使用了Leica Geosystems laser scanning solutions在两个洞穴调查中：对智利Lechuza盐洞的形态（形式和结构）变化的研究，意大利的自然井冰洞。

Santagata explains how detailed scanning at intervals can offer insight into physical changes in cave environments, “Although most processes occurring in caves are relatively slow, some can be fast, such as erosion caused by flooding. These geological changes can be monitored by terrestrial laser scanning surveys and measured by comparing ‘before and after’ 3D models. It’s an interesting tool for making comparisons over time and is therefore increasingly being used in the study of climate change.”

Measuring changes caused by flooding in the Lechuza cave (Cordillera de La Sal)

靠近智利村庄圣佩德罗·德·阿塔卡马（San Pedro de Atacama）是一个重要的洞穴，由寡西新世矿物沉积物岩石组成，被称为Cordillera de la Sal。Two surveys carried out in 2015 and 2018 allowed Santagata’s team to verify and measure small topographical changes in the cave due to a flood in 2017, which caused the river in the cave to flow and dissolve a measurable amount of halite - commonly known as rock salt.

In 2015, a complete 3D survey of the cave was organised byLa Venta Esplorazioni Geografiche以及Trieste的Grotte Eugenio Boegan委员会。该团队使用Leica HDS7000基于阶段的激光扫描仪进行大约50次扫描。2018年，La Venta团队与博洛尼亚大学合作使用了Leica ScanStation P40进行68次扫描，包括在洞穴上游的外部峡谷中进行调查的大约200米，这是国家地理学会支持的研究项目“阅读盐洞”的一部分。

Lechuza data obtained in point cloud file format was subsequently analysed to identify areas where changes had occurred. Santagata explains, “Since very limited variations were found, it was necessary to recognise points in common and position the point clouds in the same origin and orientation to make comparisons. In at least three areas of the cave, collapses from the ceiling and erosion on the floor were recognised and digitised to obtain detailed sections of these parts of the cave. The comparison between these two surveys has shown that in this case, it was possible to accurately document the areas where detachments or torrential erosion occurred.”

The natural well ice-rock cave monitoring project: measuring ice collapses

The second study concerns the underground ice deposit in the Cenote Abyss, one of the deepest and most voluminous caves of the Italian Dolomites. The 280metre-deep ice cave was discovered in 1994 after the entrance opened as a result of the abrupt emptying of a small lake in the Regional Park of Fanes, Sennes and Braies. The cave’s vertical entrance consists of a massive 130metre-thick layered ice deposit; at the lower limit of the ice-filled entrance part a shaft opens – ice-free and 165 metres deep – leading into a dome-shaped chamber occupied by a cave rock glacier.

激光扫描2015年进行的调查,2016年nd in 2018 allowed Santagata’s team to estimate variations due to collapses and acquire data for a complete monitoring project. The first expedition in October 2015 included a complete 3D laser scan survey of the final chamber using a HDS7000 phase-based laser scanner. This survey has provided the detailed volume of the chamber (420,000 m³) as well as a first record of the position of the ice masses hanging from the ceiling and of the rock glacier at the bottom. During this expedition and in subsequent ones in 2016 and 2018, other parts of the cave were 3D scanned using a ScanStation P40.

桑塔加塔（Santagata）解释说：“由于接下来的几年中的一些段落填充了一些段落，因此不可能重复对最终会议厅的调查（这将是未来探险的目标）。但是，这些年来，在洞穴上部获得的数据使我们能够研究入口附近前两个房间发生的变化。特别是，一个区域突出了崩溃，导致通道扩大。2016年之后发生了通道。该区域在倒塌之前和之后进行了3D扫描，获得的数据使我们能够验证分离并量化岩石的体积并量化了崩溃的岩石量。。”

使用两种不同的方法比较了点云：首先，我们进行了两个数据集之间的快速比较，以了解将我们更详细的分析集中在哪里。其次，我们提取了感兴趣领域的几个“切片”。我们向这些区域出口以进行完全数字化，以更好地估计岩石倒塌的量，约为61m³。”

Ongoing studies: Using 3D models to understand geological processes

The studies show that 3D laser scanning is a useful measuring technique for highlighting changes to natural structures. The data obtained can be used to help interpret other geological information, Santagata says, “For example, the variations highlighted by comparing the Lechuza cave studies provided interesting data that can easily be correlated to the rainfall that occurred in this area between the two survey campaigns.”

“In the case of the Cenote Abyss, the collapses probably occurred due to temperature variations, considering that the area is subject to oscillations between surface and cave temperatures recorded by temperature and air pressure sensors installed in the cave. A detailed environmental monitoring of this area of the cave is ongoing and the repeated 3D models will allow us to understand if these processes are important for the origin and development of ice caves in the Alps.”

探索3D中的项目：
Atacama盐洞
Atacama 3D型号
Cenote 2018 Expedition
Cenote 3D Models

Key people involved in the surveys: Tommaso Santagata (Vigea - Virtual Geographic Agency andLa Venta Esplorazioni Geografiche), Umberto Del Vecchio (Vigea - Virtual Geographic Agency andLa Venta Esplorazioni Geografiche), Jo De Waele (University of Bologna and La Venta), Francesco Sauro (University of Bologna and La Venta), Stefano Fabbri (University of Bologna/La Venta).

The Lechuza cave expeditions were organised by the Association La Venta Esplorazioni Geografiche with the scientific support of the BIGEA Department of the University of Bologna and with the collaboration of the Commissione Grotte E. Boegan in 2015. The scientific expedition in 2018 received funding from the National Geographic Society and was realised with the support of CONAF Chile. The Cenote monitoring is a multidisciplinary project organised as part of the Inside the Glaciers project with the collaboration of La Venta, BIGEA and the Regional Park of Fanes Sennes and Braies with the collaboration of Studio GST and Eli Friulia, the Speleo Club Proteo of Vicenza, the Gruppo Grotte Treviso and the Gruppo Speleologico Padovano.