世界上最快的GNSS RTK ROVER上的问答：Leica GS18T

Xiaoguang Luo博士，Stefan Schauflerand伯恩哈德·里希特（Bernhard Richter）讨论GNSS和惯性测量单元（IMU）中传感器融合领域的最新发展。新的Leica GS18 T GNSS RTK Rover结合了GNSS和IMU，以自动从Plumb中调节极点倾斜。发现这如何提高生产率，扩展RTK的适用性并减少人体错误。

目前常规RT的挑战是什么K surveying?
需要用圆形气泡手动平整杆，并将相中中心位置降低到杆尖（通过考虑天线相中中心的偏移和杆的长度），从而为用户带来了许多缺点：

• In terms of productivity, levelling the pole takes time, particularly in stakeout where it needs to be repeated iteratively.
• With respect to accuracy, holding the pole vertically is influenced by human errors and instrumental imperfections, such as a misadjusted bubble.
• Regarding applicability, it is not always possible to hold the pole vertically on a target point, for example, when measuring building corners.

In terms of solving the user’s problems: what are the major advantages of the Leica GS18 T?
新漫游者有几个好处：

• 没有现场校准
• 免疫磁性干扰
• 适用于大倾斜角度
• 标题为3D可视化

新的Leica GS18 T GNSS RTK Rover结合了GNSS和IMU，从Plumb自动调整Pole tilt，从而提高了生产率，可扩展RTK的适用性并减少人体错误。它可以提高整体用户体验。

图1 -Leica GS18 t GNSS RTK ROVER带有Leica CS20场控制器。

How does the Leica GS18 T rover answer the growing demand for speed onsite?
The definition of being “the world’s fastest GNSSS RTK rover” is based on three pillars:基于IMU倾斜补偿technique结合instantaneous RTK. This enables the highest productivity (accuracy & reliability – particularly in topographic surveys) and provides similar accuracy as measurements taken by levelling the pole manually. Due to tilt compensation, there is no need to level the pole, which increases productivity by an average of 20 per cent over conventional GNSS RTK surveying practices. In addition, the GS18 T utilises high-rate accelerations and angular velocities from MEMS IMU to determine the attitude of the pole in real time. Since these IMU measurements are not affected by magnetic fields, the GS18 T is immune to magnetic disturbances and does not require any time-consuming on-site calibrations. It works out of the box and is faster than magnetometer-based systems.

图2 -Leica GS18 T是最快的GNSS RTK ROVER，具有基于IMU的倾斜补偿。

There is always the question of accessing difficult targets – such as building corners and obstructed points?
使用GS18 t这不再是一个挑战。由于基于IMU的倾斜补偿，以前无法使用GNS访问的目标，现在也可以直接用RTK来测量，即使在超过30度的较大倾斜角度上也可以直接测量。带有好处高级信号跟踪，GS18 T特别适合RTK应用，例如，在叶子下或在城市峡谷中，在靠近树线附近运行的天空。通过应用基于IMU的倾斜补偿在GS18 t中，只要跟踪足够数量的GNSS卫星即可提供高精度RTK溶液，最大倾斜角就没有限制。Large tilt angles是过去的问题。GS18 T适用于隐藏点测量值（例如，隐藏的角落或部分被停放的汽车阻塞）。

Would this then directly impact the safety aspect while measuring in a potentially dangerous survey environment?
确切地说 - 不必专注于平整杆子，用户可以更多地关注自己的安全。通过车辆和操作机的风险大大降低了。此外，态度信息用于通过自动更新周围环境的3D可视化（取决于传感器方向）来帮助用户在现场中定位自己。

Figure 3 - Using the Leica GS18 T to measure building corners and obstructed points that were previously not measurable in conventional RTK surveying with a vertical pole.

It seems that you have successfully integrated two navigation sources, GNSS and INS?
航空航天行业长期存在的综合GNS/INS导航系统现已在调查应用程序中提供。这总结了成功的整合：

Figure 4 - Schematic and simplified illustration of the GNSS/INS integration implemented in the Leica GS18 T.

不断进行GNSS和INS之间的一致性检查，以实现可以应对极端动力学（例如硬冲击）的强大系统。由于倾斜度计算位置的计算无磁力计测量值，因此GS18 T不受磁干扰的影响。

When directly comparing conventional RTK vs. tilt compensation RTK – have you performed tests to demonstrate the practical advantages?
To demonstrate the benefits of using tilt compensation, the GS18 T was benchmarked against Rover A under open sky and strong multipath conditions. In the open-sky test (Fig. 12), two known points P1 and P2 that are separated by 8 m were measured alternately in the instantaneous mode for 10 minutes. Using Rover A, the pole needs to be levelled precisely before taking an instantaneous measurement, which is not necessary for the GS18 T due to tilt compensation. The number of measured points within 10 minutes represents a simple indicator for productivity.

图5 -RTK性能在开放天空下的基准测试，通过在瞬时模式下测量两个点10分钟（Rover A与GS18 T，极长：1.800 m）。

Figure 6 - RTK positioning test in a strong multipath environment (pole length: 1.800 m) (a) Survey marker near a building with metal facades, (b) Tilt compensation RTK measurement with the Leica GS18 T.

表1总结了开放基测试的生产率和准确性的结果：

Table 1 - Comparison of the number of measured points within a 10-minute period and the resulting rms errors between GS18 T and Rover A (open sky, pole length: 1.800 m, instantaneous measurement).

Without the need to level the pole, the GS18 T significantly reduces the time spent on a measurement, and thus increases the number of measured points by 33 per cent from 57 to 76 within a 10-minute period. In the tilt compensation case, despite the additional error from attitude determination, the 3D rms error is only 3 mm larger when compared to Rover A and amounts to 2.4 cm, which is acceptable for most topographic surveys.

Table 2 summarises the results regarding availability, accuracy and reliability:

表2-比较强大的多径环境（极长：1.800 m，瞬时测量），RTK固定位置的可用性，准确性和可靠性。

使用倾斜补偿的GS18 t，与使用RoverA的常规RTK相比，RTK固定溶液的可用性增加了15％，平均提高了定位精度，平均提高了50％。可靠性给出了以下百分比，即位置误差小于CQ的三倍，水平组件的最多可略高于6％。还请记住，这种强大的多路径环境被认为是极端情况，并且远远超出了与准确性和可靠性规格相关的标准条件。此外，无法用漫游者A测量距建筑物的10厘米的距离更接近建筑物，因为在这种情况下，不可能在目标点处将极点平衡。

Cars, power lines and buildings with structural steel – every surveyor faces these and further local magnetic disturbances on a daily basis. Does the new Leica GS18 T offer a solution to this problem?
The answer is simple: apart from no need of on-site calibrations, one major advantage of the IMU-based tilt compensation over the magnetometer-based approach is the immunity to magnetic field disturbances. We have compared two rovers under magnetic disturbances. Looking at the rms errors summarised in Table 5, the 2D accuracy of GS18 T is approximately 2 cm better than that of Rover B, whereas the 1D accuracy is at a similar level:

表3-在磁性干扰（停车场，极长：1.800 m，1 -S静态测量）下，GS18 T和RM之间的RMS误差的比较。

查看表3中总结的RMS误差，GS18 T的2D精度比Rover B好约2 cm，而1D精度在相似的水平上。

By comparing the 2D errors in Fig. 7a, the GS18 T provides higher accuracy and consistency than Rover B. Moreover, the 2D CQ estimates agree with the 2D errors, reflecting the positioning accuracy in a realistic manner. Regarding the results from Rover B in Fig. 7b, the 2D CQ values are significantly larger than the 2D errors if magnetic disturbances are detected, indicating unreliable tilt-compensated solutions. In this case, the user needs to repeat the measurement or to switch to the conventional RTK mode, which decreases productivity. Under certain circumstances, for example, when measuring points at larger tilt angles, the user would not be notified by a magnetometer-based system that the displayed accuracy cannot be achieved.

Figure 7 - Comparison of the 2D position errors and CQ between GS18 T and Rover B under magnetic disturbances (parking lot, pole length: 1.800 m, 1-s static measurement).

包括标题为3D可视化在内的如何改善整体用户体验？
By incorporating the sensor heading into 3D visualisation, the user can easily orientate himself in the survey environment and quickly move toward the target points, improving user experience and productivity.

Figure 8 - Example of heading-aided 3D visualisation when staking points with the Leica GS18 T (open sky, pole length: 1.800 m)(a) Navigation view, (b) View towards west, (c) View towards south, (d) View towards east.

Fig. 8 illustrates how the heading information helps when staking points with the GS18 T in the navigation view. If the stakeout point is more than 0.5 m away, the view shows the surroundings in the heading direction and follows the sensor from above and behind (Fig. 17a). The 3D view and stake instructions update automatically according to the current position and sensor heading, which changes from westward over southward to eastward in this example.

用您自己的话来说，与其他RTK Rovers相比，您如何总结GS18 T的总体优势？
从用户角度来看：使用倾斜补偿, instantaneous measurement provides a similar accuracy level as static RTK measurement, along with a favourable节省时间的效果.

与传统的RTK相比，带有垂直杆，倾斜的RTK显着increases productivity最多33 per centand considerablyimproves the near-building positioning performanceregarding availability and accuracy.

On a parking lot withmagnetic disturbances, the IMU-based tilt compensation producesmore accurate positions and more realistic CQ而不是基于磁力计的方法。

The IMU-based tilt-compensating RTK is applicable at大倾斜角of more than30度，3D positioning accuracy of 2 cm仍然可以实现。

By合并传感器进入3D可视化of the surroundings, the user can easily orientate himself in the surveying environment, which improves productivity and user experience.

Theattitude information倾斜补偿的RTK测量是完全可追溯，为用户自己和客户提供质量保证。

了解更多有关Leica GS18 t, please visit:Leica-Geosystems.com/GS18T

有关高性能GNSS信号跟踪的深入信息，倾斜补偿RTK和高级信号跟踪技术的挑战，请下载白皮书。