GPS World

Tag: inertial integration

  • Expert Opinions: Integrating inertial tech with GNSS

    Q: What key aspects should product designers consider when integrating inertial technology with GPS/GNSS?

    Jeremy Davis, Director, VectorNav Technologies

    A: The availability and quality of GPS in the application is critical. Industrial-grade MEMS IMUs can provide survey-grade performance when high-quality GPS is continuously available, but even tactical-grade MEMS cannot provide more than a couple of minutes of GPS-denied navigation. The level of integration between the two technologies is also important. Even comparing two systems using the same sensors, the performance is highly dependent on the ability of the system designer to leverage their respective strengths.

    Ryan Dixon, Chief Engineer, SPAN, NovAtel

     

    A: Successful integration of inertial sensors with GNSS requires understanding both the goals and environment of the application. Consider the required accuracy of attitude and position, severity of GNSS obstructions, expected dynamics and environmental conditions. Tradeoffs in size, power and cost narrow the choices, but achieving the desired performance is more nuanced. Data sheets for IMUs can also be notoriously difficult to compare. My advice is to focus on the goals and listen to the experts.

    Andrey Soloviev, Principal, Qunav

    A: There is a clear need for reliable consumer-grade GNSS/INS in GNSS-degraded environments. In this case, two key aspects are: removal of measurement outliers, mostly caused by multipath; and adequate modeling of inertial errors. The first aspect is efficiently addressed via residual monitoring, especially with GNSS carrier phase. A 15-state INS error model is generally sufficient. Yet, modeling parameters and contribution of other terms such as axis misalignment must be evaluated using test data.

  • Expert Opinions: Promising aspects of inertial integration with GNSS

    Q: What is the most promising new aspect of inertial integration with GNSS that product developers and end users should be aware of?

    Tony Rios, director, engineering systems, Systron Donner Inertial

    A: Integration with GNSS and other sensors in most every military vehicle or weapon-control system will enable inertial sensor developers to focus on driving improvements in performance for the two fundamental parameters that a sensor-fusion INS filter cannot estimate: noise and in-run bias stability. Ultra-tightly coupled sensor fusion of GNSS with range-, speed- and video position-sensing, with tactical and navigation grade inertial sensors optimized for noise and in-run, will enable design of robust GPS chip-level solutions for high-dynamic, high-performance navigation for nearly any military environment or engagement.

    Michael Whitehead, chief technology officer, Hemisphere GNSS

    A: Previously used for military applications, inertial technology has become mainstream as performance-to-cost has improved with the emergence of low-cost microelectromechanical systems (MEMS). Precise point positioning (PPP) advancements have driven GNSS accuracies to 4 cm or better, but long PPP initialization times are problematic in challenging environments where reconvergence is often required. Tightly coupled integration of PPP and navigation-quality MEMS will overcome limitations of both technologies, yielding high accuracy with high availability, even in challenging environments.

    Chris Wheeler, manager, telematics and connected sites, Trimble Navigation

    A: The availability of multi-frequency GNSS receivers with inertial components on a small lightweight board can now deliver centimeter-accurate INS/GNSS solutions, so that OEMs and integrators can significantly improve reliability and robustness in harsh or GNSS-denied applications or for solutions such as UAVs. The advances provided by MEMS inertial components increase overall efficiency by reducing the number of ground control points while still meeting the needs for a low weight and power consumption solution.