3D中的地球内部

欧洲航天局的记者特别

As a child, Tommaso Santagata, speleologist and expert in 3D cave mapping, would have never imagined that he would test some of the newest and most innovative 3D-scanning technologies for future space exploration. In 2017, he spent five days of intense mapping in Lanzarote, Spain, during the PANGEA-X (Planetary ANalogue Geological and Astrobiological Exercise for Astronauts) an European Space Agency (ESA) Spaceflight Analog field campaign. While the first results from that pioneering course keep flowing in, the adventurous speleologist has produced thelargest 3D scan of a lava tube on Earth。

他与地质学家Umberto del Vecchio和Marta Lazzaroni一起绘制了大部分熔岩管系统，作为由Lanzarote和意大利Padova大学支持的项目的一部分。最终的地图非常详细，帮助当地机构保护这种地下环境。它还提供了科学数据来研究管子的起源及其特殊的地层。

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地形

The PANGEA-X expedition ventured into the “La Cueva de los Verdes” lava tube in the Spanish island of Lanzarote, one of the world’s largest volcanic cave complexes with a total length of about 8 kilometres. The cave has both dry and water-filled sections.

熔岩管的6公里干部分具有自然的开放天窗，或Jameos正如当地人所说的那样，它们沿着洞穴路径对齐。其中一些洞穴足够大，可以容纳住宅街道和房屋。

These formations are similar to those found on Mars and on the moon. Being underground structures, they offer good shelters from radiation. This similarity makes Lanzarote a great environment to train astronauts and simulate space exploration.

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Why 3D mapping inside a cave?

当发现新的环境时，映射该区域始终是探索的第一个起点。这也适用于其他行星的任务，其中一个主要目标是选择设置大本营的地方。

Lava tubes are environments with a constant temperature, shielded from cosmic radiation and protected from micrometeorites, providing safe habitats for humans.

Precisely measuring the geometry of lava caves will allow scientists to improve their models and better understand their evolution on other celestial bodies.

由于这些原因，学习如何在地球上绘制熔岩管正在帮助探索地球。ESA宇航员Matthias Maurer加入了探险队，测试Leica Geosystems开发的两种不同的乐器，Leica Pegasus：背包和Leica BLK360。

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移动映射

Leica Geosystemsmobile mapping team trained Maurer on how to operate the Pegasus:Backpack in just 20 minutes.

The astronaut walked through the difficult terrain and checked the results on the spot through a tablet. He performed his cave-mapping mission by walking along the tube and back to compare the accuracy of the data.

“Hiking and performing geological mapping with the high-tech backpack was easy and efficient. I can perfectly see it integrated in our spacesuits for future exploration missions to the Moon or Mars,”said Maurer.

Pegasus：背包同步通过五个摄像机和两个3D成像激光镜（激光等效）收集的图像。它可以在不可用的卫星导航（例如洞穴中）进行准确的映射。

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The missions

The team did two different acquisitions with the Pegasus:Backpack to test all the positioning technologies embedded in this solution. Both missions were processed with the Leica Pegasus Manager software.

1.融合 Simultaneous Localisation and Mapping (SLAM) mission

从室外良好的GNSS条件开始，然后在挑战性GNSS条件下进行室内，具有非常低或零卫星的覆盖范围，并以良好的GNSS条件完成了任务户外。对于此类任务，团队使用了多种定位技术：GNSS +惯性测量单元（IMU） + SLAM。处理软件自动识别任务的不同阶段。

The Pegasus:Backpack, the first position-agnostic solution, could track Maurer’s movements during the data acquisition, and the IMU recorded them 125 times per second. This way, the team obtains a first good trajectory with greatest accuracy at both the beginning and the end of the mission. The team needed to re-enforce the calculation for the part with zero satellites coverage using SLAM. At this stage, no pictures or point clouds are created. The part of the mission without any GNSS information used the trajectory obtained in the previous step as an input value to process the SLAM algorithm. The result is an improved trajectory with an estimation of the positioning error where point clouds, pictures orientation and spherical views are generated.

2.The pure SLAM mission

A pure SLAM mission is typically a mission in GNSS-denied environments, like buildings, caves and tunnels. The main positioning sensors used for this type of mission are the compass, the IMU and SLAM Only LiDAR (So LiDAR). Putting the parameters correctly, the complete mission could be单击一次处理。A basic trajectory of the Pegasus:Backpack was processed using information from the compass and the IMU. The complete mission uses this first trajectory as an input value to process the SLAM algorithm. Point cloud and pictures orientation and spherical views are generated with this trajectory.

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3D laser scanning

在兰萨罗特,熔岩管一般t一起发展unnels on different levels due to lava flowing over multiple eruptions and following cracks and crevasses left from previous eruptions. It is not always possible to access the upper levels without climbing equipment.

As part of the CAVES 2016 training course, the team used photogrammetry – getting precise measurements and 3D data from at least two photographs – as a good alternative. However, photogrammetry cannot always guarantee good results, especially without the right light conditions.

要解决这些问题,PANGEA-X运动测试工程师ted the BLK360, the smallest and lightest imaging scanner on the market. The Leica Geosystems team operated it in set positions, obtaining360° images of the environment in just three minutesby pressing one button and aligning the scans directly through a tablet app.

在less than three hours，两种仪器的数据都获得了一个完整的3D模型熔岩管的1.3公里。

The PANGEA-X campaign used two of the latest Leica Geosystems technologies for a demanding mission. Both technologies provided valuable information and accurate data to map areas in a short period of time where satellite navigation was unavailable.

A version of this story first appeared in the European Space Agency blog.