3D中的地球内部

Special to the Reporter from the European Space Agency

小时候，3D洞穴映射的Speleists兼专家Tommaso Santagata从未想象过他会测试一些最新，最具创新性的3D扫描技术，以进行未来的太空探索。2017年，他在欧洲航天局（ESA）太空飞行模拟现场运动中在西班牙兰萨罗特（Lanzarote）度过了五天的密集映射。虽然该开创性课程的第一个结果不断流入，但冒险的speleoloks已经产生了largest 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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为什么要在洞穴内进行3D映射？

When a new environment is discovered, mapping the area is always a first starting point of exploration. This also applies to missions to other planets, where one of the main objectives will be to choose places to setup base camp.

熔岩管是具有恒定温度的环境，免受宇宙辐射的屏蔽，并免受微量历史的保护，为人类提供了安全的栖息地。

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 Geosystems移动映射团队在短短20分钟内就如何操作Pegasus：背包培训了Maurer。

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,”莫勒说。

The Pegasus:Backpack synchronises images collected by five cameras and two 3D imaging LIDAR profilers, the laser equivalent of radar. It enables accurate mapping where satellite navigation is unavailable, such as in caves.

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任务

该团队使用Pegasus：背包进行了两次不同的收购，以测试该解决方案中嵌入的所有定位技术。这两个任务均使用Leica Pegasus Manager软件处理。

1.融合 Simultaneous Localisation and Mapping (SLAM) mission

Starting from the outdoor with good GNSS conditions then going indoor in challenging GNSS conditions with very low or zero satellites coverage and finishing the mission outdoor with good GNSS conditions. For this type of mission, the team used multiple positioning technologies: GNSS + Inertial Measurement Unit (IMU) + SLAM. The processing software recognised automatically the different phases of the mission.

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

一个纯粹的大满贯任务通常是一个在GNSS的使命-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激光扫描

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.

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.

To solve these problems, the PANGEA-X campaign tested 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 minutes通过按一个按钮并直接通过平板电脑应用对齐扫描。

在less than three hours, data from both instruments obtained a complete 3D model of a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.