Q&A on the world’s Fastest GNSS RTK Rover: Leica GS18T

Dr. Xiaoguang Luo, Stefan Schaufler和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。

常规RTK测量的当前挑战是什么？
The need of manually levelling the pole with a circular bubble and the phase centre position being reduced to the pole tip (by considering the antenna phase centre offset and the length of the pole), result in a number of disadvantages for the user:

• 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？
There are several benefits of the new rover:

• 没有现场校准
• 免疫磁性干扰
• Applicable at large tilt angles
• Heading-aided 3D visualisation

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，从而提高生产率，扩展RTK的适用性并减少人体错误。它改善了整体用户体验无法比较。

Figure 1 - Leica GS18 T GNSS RTK rover with Leica CS20 field controller.

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:IMU-based倾斜补偿技术结合瞬时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.

Figure 2 - Leica GS18 T as the fastest GNSS RTK rover with the IMU-based tilt compensation.

总是有一个问题的问题，例如建立角落和障碍物？
With the GS18 T this is not considered a challenge anymore. Due to the IMU-based tilt compensation, the targets that were previously not accessible with GNSS, can now directly be measured with RTK, even at large tilt angles of more than 30 degrees. With the benefits ofadvanced signal tracking，GS18 T特别适合RTK应用，例如，在叶子下或城市峡谷中，在靠近树线附近运行的天空。通过应用IMU-based tilt compensation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 anglesare a problem of the past. The GS18 T is applicable to hidden point measurements (for instance hidden corners or points partly blocked by parked cars).

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，用户可以更加关注自己的安全。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（取决于传感器的方向）来帮助用户在现场取代自己。

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？
Integrated GNSS/INS navigation systems which have long existed in the aerospace industry are now available in surveying applications. This sums up the successful integration:

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.

Figure 5 - RTK performance benchmarking under open sky by measuring two points alternately in the instantaneous mode for 10 minutes (Rover A vs. GS18 T, pole length: 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：

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:

Table 2 - Comparison of the availability, accuracy and reliability of RTK fixed positions between GS18 T and Rover A in a strong multipath environment (pole length: 1.800 m, instantaneous measurement).

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％。可靠性给出了一个百分比，即位置误差小于CQ的三倍，水平组件的最高可增强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对建筑物的距离更接近10厘米，因为在这种情况下，不可能在目标点处将极点平衡。

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:

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。

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。

用您自己的话来说，与其他RTK Rovers相比，您将如何总结GS18 T的总体优势？
From a user perspective: using倾斜补偿，瞬时测量提供了与静态RTK测量相似的精度水平，time-saving effect.

In comparison to conventional RTK with a vertical pole, tilt-compensating RTK significantlyincreases productivityby up to33％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 CQ而不是基于磁力计的方法。

基于IMU的倾斜加固RTK适用于large tilt angles超过30 degrees，3D定位精度为2 cm仍然可以实现。

Byincorporating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.

The态度信息倾斜补偿的RTK测量是完全可追溯, enabling quality assurance for users themselves and their clients.

了解更多有关Leica GS18 T， 请拜访：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。