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 the地球上熔岩管的最大3D扫描。

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

Pangea-X探险队冒险进入西班牙Lanzarote岛的“ La Cueva de Los Verdes”熔岩，这是世界上最大的火山洞综合体之一，总长度约为8公里。该洞穴既有干燥的部分也有水。

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。

这些地层与火星和月球上的地层相似。作为地下结构，它们提供了辐射的良好避难所。这种相似性使Lanzarote成为训练宇航员并模拟太空探索的绝佳环境。

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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.

“使用高科技背包远足和执行地质映射非常容易有效。我可以完美地看到它在我们的航天服中融合在一起，以供未来的月球或火星探索任务。”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 同时本地化和映射（SLAM）任务

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。

珀加索斯:背包,第一个position-agnosticsolution, 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.纯粹的大满贯任务

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。PEGASUS：背包的基本轨迹是使用Compass和IMU的信息处理的。完整的任务使用第一个轨迹作为输入值来处理SLAM算法。点云和图片方向和球形视图是通过此轨迹生成的。

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3D laser scanning

在Lanzarote, lava tubes generally develop along tunnels 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.

作为洞穴2016培训课程的一部分，该团队使用了摄影测量法 - 从至少两张照片中获得精确的测量和3D数据 - 作为一个很好的选择。但是，摄影测量法不能总是保证良好的结果，尤其是没有正确的光条件。

为了解决这些问题，Pangea-X活动测试了BLK360，这是市场上最小，最轻的成像扫描仪。Leica Geosystems团队以固定位置进行操作，获得仅三分钟内的360°环境图像by pressing one button and aligning the scans directly through a tablet app.

在少于三个小时，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。

Pangea-X活动使用了两种最新的Leica Geosystems Technologies进行苛刻的任务。这两种技术都提供了有价值的信息和准确的数据，以在不可用的卫星导航的短时间内绘制区域。

这个故事的一个版本首先出现在欧洲航天局博客中。