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

Despite being hundreds of thousands of kilometres apart, the island of Lanzarote and the Moon share remarkable similarities. The Spanish island, belonging to the Canary archipelago in the Atlantic, is home to the world’s largest volcanic cave and exceptional scenery that resembles the lunar landscape. So much in fact that the island has been chosen as a location for astronaut training ahead of space missions. More recently, Lanzarote’s Corona lava tube has helped prepare teams at the European Space Agency to explore and study caves of similar characteristics observed on the Moon and on planets like Mars.

As a result of the latest advancements and innovation in geospatial technology, several field surveys were conducted in 2017 led by Tommaso Santagata from the Virtual Geographic Agency维亚, deploying3D Terrestrial Laser Scanning(TLS) andMobile Mapping solutions, resulting in the first ever 3D replica of the largest lava tube on Earth.

Exploring the depths of the Corona lava tube

位于兰萨罗特岛以北,日冕熔岩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.

In order to successfully execute this project, various field surveys were completed over the course of a year deploying a variety of Leica Geosystems solutions, including theLeica HDS7000,Leica ScanStation P40andLeica BLK360激光扫描仪以及Leica 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.

Capturing every detail with the latest laser scanning technology

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.

Leica Pegasus的准确性和机动性提高：背包

To generate an even more detailed 3D map, a survey was performed using the Pegasus:Backpack mobile mapping solution. Designed to capture 3D data in overground and underground environments, with images and point clouds collected by five cameras and two LiDAR profilers. Its lightweight and ergonomic structure allowed teams to comfortably navigate the difficult terrain and to instantly visualise the data on a handheld tablet computer.

“由于熔岩管系统的复杂和地下性质，Pegasus：Backpack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 — theLeica Cyclone3D point cloud processing office software was then deployed to align the scans and process a unified point cloud of the cave,” says Santagata. “Once the 3D map was available in a single point cloud, several outputs were generated as topographic maps with plans and sections of the lava tube.” In addition, the data was subsequently used to produce comparisons with other lava tubes on earth, with the objective of studying similar features on the Moon and Mars — this operation was performed using theAutodesk AutoCAD2017 software.

除了对未来太空任务的科学目的和培训外，数据还用于生产多媒体和交互内容，例如视频动画，虚拟现实和桌面应用程序，显示了更广泛的公众是Corona熔岩管系统中鲜为人知的部分。只有有限的部分向Cueva de Los Verdes和Jameos del Agua开放。此外，该项目的结果是在Cabildo de Lanzarote在2019年组织的旅游洞穴管理期间提出的，该洞穴在2019年安装了一个虚拟现实立场，向公众展示了洞穴。

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-FríasJ。，Smets L.M.，GómezG.D。，Massironi M.（2019）兰萨罗特的火山洞：一种自然实验室，用于了解火山孔隙遗传学过程和行星洞穴。在Lanzarote和Chinijo群岛地质公园中：从地球到太空（第125-142页）。施普林格，康。

SAURO F, POZZOBON R。DE BERNARDINI MASSIRONI MS P., SANTAGATA T., DE WAELE J. (2020)地球，月亮和火星上的熔岩管：比较行星学揭示其大小和形态的评论. Earth Science Reviews 103288.