视觉惯性系统（VIS）技术

Some years ago, during our technology screening process at the Hexagon Technology Centre, we identified the development need for Visual Simultaneous Localization and Mapping (SLAM) technology for the Hexagon group. It was clear from the beginning that this technology could be applied to determine the position of devices in 3D-space and would be highly beneficial for future innovations. We started with the first implementation of a generic Visual SLAM algorithm and investigated the potential of this technology for various applications relevant to our business areas.

What is Visual SLAM?

In principle, Visual SLAM is nothing more than a repetitive application of resection and forward-intersection with an optional bundle-adjustment at the very end. These basic algorithms are well known from photogrammetry for more than a century. However, the developments in feature tracking and feature matching triggered by computer vision and robotics – that made the manual selection of tie points obsolete – enabled the implementation of an automated workflow.

Navigation through 3D-space based on Visual SLAM is quite intuitive. It works quite similar to how us humans navigate through the world. When we walk towards an object, e.g. a building, the object gets larger in our field of view. When we walk backwards, it gets smaller.

在Visual Slam中，功能跟踪是在图像流中检测点特征（或所谓的地标），并跟踪其从一个图像框架到另一个图像框架的位置。现在，当相机向建筑物移动时，检测到的功能，例如由于建筑物在视野中变大，因此建筑物或门或窗户的角将从图像中心向外移动。当相机从左向右旋转时，图像上的特征将向右移动和左侧。因此，从图像流的框架之间的特征点的运动中，Visual Slam可以在3D空间中推导相机的运动方向。

In a continuous process, the SLAM algorithm computes the 3D-coordinates (mapping) of the tracked features from two or more positions and uses these coordinates for the determination of the following position (localisation). The generated map of landmarks is evolving as the operator moves along this track to the next scanner setup and acts as a reference for the whole positioning algorithm. Consequently, this map that is built up and maintained during the process is essential to keep the drift error small.

仅基于惯性测量，有其他方法。惯性测量单元（IMU）提供了对加速度和角度速率的测量值，这些速率和角度速率集成以在设备的第一步，最后定位和方向。由于这些测量值受测量误差的影响，因此整合会导致衍生数量的显着漂移。由于在这种方法中缺少图作为整体参考，因此所得的漂移显着高于视觉大满贯。虽然，仅基于惯性测量值无法实现最佳结果，但IMU的数据可以与图像测量结果融合并支持视觉猛击。

视觉大满贯如何重新定义注册过程？

激光扫描的典型注册，即单个扫描与一个组合点云的组合，是在使用后处理软件在办公室进行完整的数据后执行的。在办公室时，通常是操作员第一次能够调查扫描项目的结果并检查数据采集的完整性。操作员可能会识别一些缺失的区域，他们可能必须返回站点并进行其他扫描。有时，如果项目位置远离办公室的情况，则可以与一段时间的开车相关联，因此，客户希望不惜一切代价避免使用。

In-field pre-registration of several laser scans was the new feature that Juergen Mayer, business director for terrestrial laser scanning at that time had in mind, which would solve costly rework completely. After each scan, the intention was for acquired data in the field to be automatically registered with the previous scan data acquired. The resulting combined point cloud should then be visualised on a mobile tablet computer. This would allow the customer to immediately investigate what data is captured and what data could be missing, to optimally plan the next scanner setup and, above all, to perform a completeness check when still on site.

This was discovered during our feasibility study and finally we could show that the concept would work in practice as well. Based on these findings, together with our colleagues from the business unit, the development of the product started and ended with the announcement of theLeica RTC360在HXGN Live 2018。

Visual Slam可以成为此新的现场注册功能的基础吗？

从理论上讲,我t was obvious that based on Visual SLAM, the motion between two scanning setups should be determined. Knowing the translation and rotation, the point cloud resulting from the current scan can automatically be aligned with the point cloud from the previous scan. The goal was to then prove that the concept would work in practice.

视觉惯性系统（VIS）技术不应在当时进行的激光扫描工作流程上添加任何约束。这意味着操作员不应受到一些其他规则的影响，例如以特定方式携带激光扫描仪。这是可行性研究开始的主要要求之一。即使RTC360的一侧被阻塞，例如在操作员的主体上，VIS技术仍应起作用。从根本上讲，这是RTC360中内置五个VIS相机的主要原因。此外，应实时进行自动预注册的处理，以使操作员在执行下一次扫描后立即获得结果。鉴于此，我们的视觉大满贯算法必须证明它可以很好地整合到陆地激光扫描的工作流程中。

下一步是什么？

同时，在六边形技术中心，已经研究了其他许多视觉bob体育报道量应用程序。尽管基本原理是相同的，它总是需要进行一些微调和适应特定设置和工作流程，以实现最佳结果。在这种情况下的一个亮点是莉卡的发展blk2go手持式成像激光扫描仪，其中视觉猛击与LiDAR SLAM结合使用，将算法提升到一个新的水平。这只是该技术证明其适用于定位工作流程的许多例子。其中一些已经作为产品发布了，将来可以预期更多的产品，从而丰富整个Hexagon GeoSystems的产品组合。bob体育报道