世界上最快的GNSS RTK ROVER：LEICA GS18T的问答

Xiaoguang Luo博士，Stefan Schaufler和伯恩哈德·里希特（Bernhard Richter）discuss the latest developments in the field of sensor fusion in GNSS and inertial measurement unit (IMU). The new Leica GS18 T GNSS RTK rover combines GNSS and IMU to automatically adjust pole tilt from plumb. Discover how this can increase productivity, extend RTK applicability and reduce human errors.

What are the current challenges of conventional RTK 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偏移和杆的长度），从而为用户提供了许多缺点：

• In terms of productivity, levelling the pole takes time, particularly in stakeout where it needs to be repeated iteratively.
• 关于准确性，垂直握住杆子会受到人类错误和工具性缺陷的影响，例如疾病的气泡。
• 关于适用性，并非总是有可能在测量建筑物角时垂直将极点固定在目标点上。

在解决用户的问题方面：Leica GS18 T的主要优势是什么？
新漫游者有几个好处：

• Free from on-site calibrations
• Immune to magnetic disturbances
• 适用于大倾斜角度
• 标题为3D可视化

新徕卡GS18 T GNSS RTK探测器将GNSS相结合和IMU to automatically adjust pole tilt from plumb, which increases productivity, extends RTK applicability and reduces human errors. It improves the overall user experience beyond comparison.

图1 -Leica GS18 T GNSS RTK ROVER带有Leica CS20田间控制器。

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IMUtilt compensation技术结合瞬时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。

总是有一个问题的问题，例如建立角落和障碍物？
使用GS18 T，这不再被认为是一个挑战。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测量，即使在超过30度的大倾斜角度上也可以直接测量。带来的好处高级信号跟踪, the GS18 T is especially suitable for RTK applications where the sky is partially visible, for example, operating close to tree lines, under foliage or in urban canyons. By applying the基于IMU的倾斜补偿of the GS18 T, there is no limit to the maximum tilt angle as long as a sufficient number of GNSS satellites are tracked to be able to provide high-precision RTK solutions.Large tilt angles是过去的问题。GS18 T适用于隐藏点测量（例如，隐藏的角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?
Exactly – without having to focus on levelling the pole, the user can pay more attention to his own safety. The risks of passing vehicles and operating machines are vastly reduced. In addition, attitude information is used to help users orientate themselves in the field by automatically updating the 3D visualisation of the surroundings (depending on the sensor orientation).

图3-使用Leica GS18 T测量建筑物的拐角和阻塞点，这些点以前在常规的RTK测量中使用垂直极是无法测量的。

看来您已经成功整合了两个导航资源，GNSS和INS？
航空航天行业长期存在的综合GNSS/INS导航系统现已在调查应用程序中获得。这总结了成功的整合：

图4- Leica GS18 T中实现的GNSS/INS集成的示意图和简化的例证。

Consistency checks between GNSS and INS are carried out constantly to enable a robust system that can cope with extreme pole dynamics, such as hard shocks. Since no magnetometer measurements are involved in the computation of tilt-compensated positions, the GS18 T is immune to magnetic disturbances.

直接比较常规RTK与倾斜补偿RTK时 - 您是否执行了测试以证明实际优势？
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（漫游者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.

Table 1 summarises the results from the open-sky test with respect to productivity and accuracy:

表1-比较10分钟内测量点的数量以及GS18 T和ROVER A之间的RMS误差（开放天空，极长：1.800 m，瞬时测量）。

GS18 t无需平整杆，可显着减少在测量上花费的时间，因此在10分钟内将测量点的数量从57增加到76。在倾斜补偿案例中，尽管态度确定有其他错误，但与Rover A相比，3D RMS误差仅大3毫米，总计2.4 cm，这对于大多数地形调查都是可以接受的。

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

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

Using the GS18 T with tilt compensation, the availability of RTK fixed solutions increases by 15 per cent when compared to conventional RTK using Rover A. The positioning accuracy is significantly improved, on average by 50 per cent. The reliability gives the percentage that the position error is less than three times the CQ, which is slightly enhanced by up to 6 per cent for the horizontal components. Please also keep in mind that such a strong multipath environment is considered as an extreme case and is far beyond the standard conditions relevant for accuracy and reliability specifications. In addition, points closer than 10 cm to a building cannot be measured with Rover A at all since in this case it is not possible to level the pole at the target point.

汽车，电源线和带有结构性钢的建筑物 - 每位测量师每天都面对这些，并进一步局部磁性干扰。新的Leica GS18 T是否为此问题提供了解决方案？
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:

Table 3 - Comparison of the rms errors between GS18 T and Rover B under magnetic disturbances (parking lot, pole length: 1.800 m, 1-s static measurement).

Looking at the rms errors summarised in Table 3, 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.

通过比较图7a中的2D误差，GS18 t比RoverB提供了更高的准确性和一致性。此外，2D CQ估计值与2D误差一致，以现实的方式反映了定位精度。关于图7b中流动站B的结果，如果检测到磁性干扰，则2D CQ值明显大于2D误差，表明倾斜度补偿的溶液不可靠。在这种情况下，用户需要重复测量或切换到常规的RTK模式，从而降低生产率。例如，在某些情况下，当以较大的倾斜角度测量点时，基于磁力计的系统不会通知用户，无法实现显示的精度。

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.

图8说明了导航视图中使用GS18 t的标题信息时的标题信息如何有所帮助。如果占用点超过0.5 m，则视图显示了沿标题方向的环境，并从上方和后面遵循传感器（图17a）。在此示例中，根据当前位置和传感器标题自动更新3D视图和赌注指令，从当前位置和传感器标题进行更新。

In your own words, how would you summarise the overall GS18 T advantages in comparison to other RTK rovers?
从用户角度来看：使用tilt compensation，瞬时测量提供了与静态RTK测量相似的精度水平，节省时间的效果.

与具有垂直极的常规RTK相比，倾斜的RTK显着increases productivity最多33％和considerablyimproves the near-building positioning performanceregarding availability and accuracy.

On a parking lot with磁干扰，基于IMU的倾斜补偿会产生more accurate positions and more realistic CQthan the magnetometer-based approach.

基于IMU的倾斜加固RTK适用于大倾斜角超过30度, where a3D定位精度为2 cmis still achievable.

By合并sensor heading into 3D visualisationof the surroundings, the user can easily orientate himself in the surveying environment, which improves productivity and user experience.

The态度信息of tilt-compensated RTK measurements isfully traceable，为用户自己和客户提供质量保证。

To learn more about theLeica GS18 t， 请拜访：www.sendai-torema.com/gs18t

For in-depth information on high-performance GNSS signal tracking, the challenges in tilt compensation RTK and advanced signal tracking technologies, please download the white paper.