Accurate navigation is required in many Unmanned Aerial Vehicle (UAV) applications. In recent years, GNSS Precise Point Positioning (PPP) has been recognised as an efficient approach for providing precise positioning services. In contrast to the widely used Real-Time Kinematic (RTK), PPP is independent of reference stations, which greatly broadens its scope of application. However, the accuracy and reliability of PPP can be significantly decreased by poor GNSS satellite geometry and outage. In response, a real-time four-constellation GNSS PPP is applied to improve the geometry in this work, and PPP is tightly coupled with an Inertial Measurement Unit (IMU) to smooth the position and velocity output, thus improving the robustness of the navigation solution. Experimental flight tests are carried out using a UAV in an open-sky area, and GNSS-challenged environments are simulated. The results show that the four-constellation GNSS PPP/IMU integration reduces the Root-Mean-Square (RMS) Three-Dimensional (3D) positioning and velocity error by 76.4% and 67.1%, respectively, in open sky with respect to the one-GNSS PPP. Under scenarios where GNSS measurements are insufficient, the coupled system can still provide continuous solutions. Moreover, the coupled PPP/IMU system can also maintain the convergence of PPP during GNSS-challenged periods and can greatly shorten the re-convergence period of PPP when the UAV returns to the open sky.

中文翻译：

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使用实时 GNSS 精确点定位和 IMU 集成为无人机实现稳健和准确的导航

许多无人机 (UAV) 应用都需要精确导航。近年来，GNSS精确点定位（PPP）已被公认为提供精确定位服务的有效方法。与广泛使用的实时动态（RTK）相比，PPP独立于参考站，大大拓宽了其应用范围。然而，糟糕的 GNSS 卫星几何形状和中断会显着降低 PPP 的准确性和可靠性。作为回应，在这项工作中应用实时四星座 GNSS PPP 来改进几何结构，并且 PPP 与惯性测量单元 (IMU) 紧密耦合以平滑位置和速度输出，从而提高导航的鲁棒性解决方案。在开阔的天空区域使用无人机进行实验飞行测试，并模拟了 GNSS 挑战的环境。结果表明，在开阔的天空中，四星座 GNSS PPP/IMU 集成将均方根 (RMS) 三维 (3D) 定位和速度误差分别降低了 76.4% 和 67.1%。 -GNSS PPP。在 GNSS 测量不足的情况下，耦合系统仍然可以提供连续的解决方案。此外，耦合的PPP/IMU系统还可以在GNSS挑战期间保持PPP的收敛，并且可以大大缩短无人机返回开阔天空时PPP的重新收敛时间。关于单一GNSS PPP，在开阔的天空中。在 GNSS 测量不足的情况下，耦合系统仍然可以提供连续的解决方案。此外，耦合的PPP/IMU系统还可以在GNSS挑战期间保持PPP的收敛，并且可以大大缩短无人机返回开阔天空时PPP的重新收敛时间。关于单一GNSS PPP，在开阔的天空中。在 GNSS 测量不足的情况下，耦合系统仍然可以提供连续的解决方案。此外，耦合的PPP/IMU系统还可以在GNSS挑战期间保持PPP的收敛，并且可以大大缩短无人机返回开阔天空时PPP的重新收敛时间。