Creating a 3D map of the world’s largest volcanic cave to aid future space missions

尽管兰萨罗特岛和月球相距数十万公里，但具有出色的相似之处。西班牙岛属于大西洋的金丝雀群岛，是世界上最大的火山洞穴和类似于月球景观的风景。实际上，在太空任务之前，该岛被选为宇航员训练的地点。最近，Lanzarote的Corona Lava Tube帮助了欧洲航天局的团队探索和研究在月球和火星等行星上观察到的类似特征的洞穴。

由于最新的地理空间技术进步和创新，2017年由Virtual Geographic Agency的Tommaso Santagata领导的几项现场调查Vigea, deploying3D陆地激光扫描（TLS）和Mobile Mapping solutions, resulting in the first ever 3D replica of the largest lava tube on Earth.

探索电晕熔岩管的深度

Located in the north of Lanzarote, the Corona lava tube extends over 8.5 kilometres and is made up of both dry and submerged passages, with some sections more than 25 metres wide. Although the first explorations and initial mapping began in the seventies, its real extension was practically unknown until the early sixties when the first topographic survey was carried out. This latest and most ambitious 3D scanning project, commissioned by the local government, Cabildo de Lanzarote, also implemented the latest mobile mapping technology, which is part of the European Space Agency’s training course PANGAEA-X. This training allows them to test new instruments and technologies that will be used in future space missions.

为了成功执行该项目，在一年的过程中完成了各种现场调查Leica HDS7000,Leica Scanstation P40和Leica BLK360laser scanners, as well as theLeica Pegasus：背包mobile mapping solution. The result is the largest 3D replica of a lava tube on the planet with 5.7 kilometers of cave passages mapped.

使用最新的激光扫描技术捕获所有细节

Three individual surveys and over 440 scans were completed to map the lava tube system, composed of different sections connected to each other through external collapses. These collapses were used to geo-reference the laser scanning surveys performed inside the cave on the external surface. This was made possible with Global Navigation Satellite System (GNSS) measurements, Light Detection and Ranging (LiDAR) data from the Spanish Geological Service, and through photogrammetry data obtained with unmanned aerial vehicle (UAV) flights along the cave path.

More specifically, 800 metres of the above sea level passages were mapped using the HDS7000 and an estimated five kilometres using a ScanStation P40. In addition, the BLK360 imaging laser scanner was deployed to scan an upper level of around 300 metres during the PANGAEA-X expedition.

Increased accuracy and mobility with the Leica Pegasus:Backpack

为了生成更详细的3D地图，使用Pegasus：背包移动映射解决方案进行了调查。旨在在地上和地下环境中捕获3D数据，其中图像和点云由五个摄像机和两个激光探测器收集。它的轻量级和人体工程学结构使团队能够舒适地浏览困难的地形并立即可视化手持板计算机上的数据。

“由于熔岩管系统的复杂和地下性质，Pegasus：背包被部署以获取融合的SLAM数据 - 在带有GNSS数据的户外环境中开始和结束，但在很大程度上探索了没有卫星的洞穴，”Co-Founder of Virtual Geographic Agency Vigea 3D and an expert on Lanzarote’s volcanic cave system. As the lengthiest part of the mission was carried out without any GNSS information, the second phase of the data processing was to reinforce the calculation of the path recorded using a SLAM algorithm and the information obtained by the LiDAR mounted on the Pegasus:Backpack.

Processing the data and creating the final 3D map

“Having gathered large amounts of data — 400 GB corresponding to the raw laser scanning data alone — the狮子旋风然后部署了3D点云处理办公软件以对齐扫描并处理洞穴的统一点云。” Santagata说。“一旦3D地图在单点云中可用，就会生成几个输出作为具有熔岩管的计划和部分的地形图。”此外，随后将数据用于与地球上其他熔岩管进行比较，目的是在月球和火星上研究类似的特征 - 此操作是使用该操作的Autodesk AutoCAD2017年软件。

Aside from its scientific purposes and training for future space missions, the data was also used to produce multimedia and interactive contents like video animations, virtual reality and desktop applications showing the wider public the lesser known parts of the Corona lava tube system. Only limited sections are open to the public at Cueva de Los Verdes and Jameos del Agua. Furthermore, the results of this project were presented during an event on the management of touristic caves organised by the Cabildo de Lanzarote in 2019, where a virtual reality stand was installed to show the cave to the public.

Latest expedition update: Supporting the search for “stone-eating” bacteria

In spring 2021, Santagata returned to Lanzarote to support a microbiology research project. The Tubolan project, led by Ana Miller, geomicrobiologist at the Institute of Natural Resources and Agrobiology of Seville (CSIC), was set up to study the microbial organisms living in the Lanzarote lava tube systems. The team’s findings will help those searching for life on the Moon and Mars, which also have lava systems. Although the conditions are different to those on earth, the Martian and lunar cave systems could theoretically also support chemolithoautotrophic microorganisms that survive and grow by using and transforming minerals. In the framework of the Tubolan project, Santagata used a Leica BLK360 to make scans and 360 degree videos – contributing to the study of caves’ formation and uncovering more of the caves’ geography than ever before. The amazing video footage taken can be watched onVIGEA’s YouTube channel.

进一步阅读：
SAURO F., POZZOBON R., SANTAGATA T., TOMASI I., TONELLO M., MARTÍNEZ-FRÍAS J., SMETS L.M., GÓMEZ G.D., MASSIRONI M. (2019)火山Caves of Lanzarote: A Natural Laboratory for Understanding Volcano-Speleogenetic Processes and Planetary Caves.In Lanzarote and Chinijo Islands Geopark: From Earth to Space (pp. 125-142). Springer, Cham.

SAURO F, POZZOBON R。DE BERNARDINI MASSIRONI MS P., SANTAGATA T., DE WAELE J. (2020)Lava tubes on Earth, Moon and Mars: a review on their size and morphology revealed by comparative planetology. Earth Science Reviews 103288.