Visual Inertial System (VIS) Technology

几年前，在六边形技术中心的技术筛查过程中，我们确定了六边形组的视觉同时定位和映射（SLAM）技术的发展需求。bob体育报道从一开始就可以清楚地知道该技术可以应用于3D空间中设备的位置，并且对未来的创新非常有益。我们从首次实施了通用的视觉大满贯算法，并研究了该技术对于与我们的业务领域相关的各种应用的潜力。

What is Visual SLAM?

原则上，视觉大满贯无非是重复的切除和向前交流的应用，并在最后，可选的束调整。这些基本算法在一个多世纪以来是从摄影测量中众所周知的。但是，功能跟踪和功能匹配的发展是由计算机视觉和机器人技术触发的，这使手动选择了领带的选择 - 使自动化工作流程实现了。

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.

在视觉跟踪摒弃功能是检测point features – or so-called landmarks – in the image stream and tracks their position from one image frame to the next. Now, when the camera moves towards a building, the detected features, e.g. the corners of the building, or the door or the windows, will then move from the image centre outwards since the building is getting larger in the field of view. When the camera is rotating from left to right the features on the image would then move to the right and to the left. Hence, from the movement of the feature points between the frames of the image stream, Visual SLAM can deduce the direction of motion of the camera in 3D-space.

在连续过程中，SLAM算法计算两个或多个位置的跟踪特征的3D坐标（映射），并使用这些坐标来确定以下位置（本地化）。随着操作员沿着该轨道移动到下一个扫描仪设置，生成的地标地图正在发展，并作为整个定位算法的参考。因此，在此过程中构建和维护的这张地图对于保持漂移误差较小至关重要。

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，因此积分导致派生数量的显着漂移。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大满贯。

视觉大满贯如何重新定义注册过程？

The typical registration of laser scans, i.e. the combination of the individual scans to one combined point cloud, is performed after the complete data acquisition in the office using post-processing software. When in the office, it is usually the first time when an operator is able to investigate the result of the scanning project and check the completeness of the data acquisition. It is possible that the operator identifies some missing areas and they may have to go back to the site and perform some additional scans. Sometimes, in cases where the project location is far from the office, it can be associated with a drive of quite some time and, therefore, something customers want to avoid at all costs.

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.

这是在我们的可行性研究中发现的，最后我们可以证明该概念也将在实践中起作用。基于这些发现，与业务部门的同事一起，产品的开发开始并结束于宣布。Leica RTC360at HxGN LIVE 2018.

Could Visual SLAM be the basis for this new field registration feature?

从理论上讲，很明显，基于视觉量，应确定两个扫描设置之间的运动。知道翻译和旋转，由当前扫描产生的点云可以自动与上一个扫描中的点云对齐。然后，目标是证明该概念在实践中会起作用。

The Visual Inertial System (VIS) technology should not add any constraints on the laser scanning workflow as it was carried out at that time. This means, that the operator should not be affected by some additional rules like carrying the laser scanner in a specific manner. This was one of the main requirements when the feasibility study started. Even if one side of the RTC360 is obstructed, e.g. by the body of the operator, the VIS technology should still work. Fundamentally, this is the main reason why there are five VIS cameras built into the RTC360. Moreover, the processing of the automatic pre-registration should be carried out in real-time in such a way that the operator gets the result presented immediately after the next scan was performed. Given this, our Visual SLAM algorithm had to prove that it could be nicely integrated into the workflow of terrestrial laser scanning.

What’s next?

同时，在Hexagon技术中心，还研究了其他许bob体育报道多视觉量应用程序。尽管基本原理是相同的，它总是需要对特定设置和工作流程进行一些微调和适应，以实现最佳结果。在这种情况下的亮点是莉卡的发展BLK2GOhandheld imaging laser scanner, where Visual SLAM is combined with LiDAR SLAM taking the algorithm to the next level. This is just one example out of many where this technology has proven its applicability for positioning workflows. Some of those have been released as a product already and many more can be expected in the future, enriching the entire product portfolio of Hexagon Geosystems.