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.

地质学家Umberto德尔维奇奥和集市a Lazzaroni, he mapped most of the lava tube system as part of a project supported by the Cabildo of Lanzarote and the University of Padova, Italy. The resulting map comes alive in great detail, helping local institutions to protect this subterranean environment. It also provides scientific data to study the origins of the tube and its peculiar formations.

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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.

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 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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The missions

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

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Lanzarote中，由于熔岩在多次喷发上流动，沿着先前喷发剩下的裂缝和裂缝，熔岩管通常沿着不同的隧道开发。在没有攀爬设备的情况下，并非总是可以进入高层。

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，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.