地球内部在3d

Special to the Reporter from the European Space Agency

作为一个孩子，Tommaso Santagata，Stameleogist和3D洞穴映射专家，从未想过他将测试一些最新，最具创新性的3D扫描技术，以促进未来的空间探索。2017年，他在西班牙兰萨罗特州的兰萨罗特州（Pangea-X（宇航员的行星模拟地质和纪念学生练习）欧洲航天局（ESA）航天模拟领域运动。虽然第一个结果来自于此开拓课程的效果，但冒险的洞穴学家已经产生了largest 3D scan of a lava tube on Earth.

与地质学家Umberto del Vecchio和Marta Lazzaroni一起映射了大多数熔岩管系统，作为兰萨罗特的Cabildo和意大利帕多瓦大学的项目支持的项目。由此产生的地图非常详细地活着，帮助本地机构保护此地下环境。它还提供科学数据，以研究管的起源及其特殊地层。

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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6公里的干燥部分有天然开放的天窗，或jameos.当当地人称之为它们时，沿着洞穴途径对齐。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3D在洞穴里面映射？

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，从宇宙辐射屏蔽并保护免受MicroMeteorites的保护，为人类提供安全栖息地。

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，学习如何在地球上映射熔岩管正在帮助探索地球。ESA Astronaut，Matthias Maurer加入了探险，测试了由Leica Pegasus的Leica Geosystems开发的两种不同的乐器：背包和Leica Blk360。

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移动映射

Leica Geosystems移动映射队训练有素的Maurer如何操作Pegasus：背包在20分钟内。

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,”莫雷尔说。

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

该团队与Pegasus进行了两种不同的收购：背包测试在该解决方案中嵌入的所有定位技术。两个任务都是用徕卡Pegasus经理软件处理的。

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

纯粹的Slam任务通常是GNSS拒绝环境的使命，如建筑物，洞穴和隧道。用于这种任务的主要定位传感器是指南针，IMU和仅限LIDAR（所以LIDAR）。正确地放置参数，完整的使命可能是单击处理. 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.

来解决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通过按一个按钮并通过平板电脑应用直接对齐扫描。

在less than three hours, data from both instruments obtained a complete 3D model of a1.3公里的熔岩管。

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.