What is IMU/GNSS post-processing? | Commercial UAV News

Replacing real-time positional correction, a  PPK (Post-Processing Kinematic) software resolves errors and applies precision corrections following the completion of a mission. This advanced software not only enhances the overall quality of an acquisition but also addresses data loss incurred during surveys or installation errors. It proves to be a crucial tool, capable of saving the day.

Mainly used with high-end GNSS-aided INS systems , post-processing has evolved to be accessible across a spectrum of surveying applications: Laser Ring Gyro Price

What is IMU/GNSS post-processing? | Commercial UAV News

How does Post-Processing Work in Inertial Navigation  Systems (INS)? In an Inertial Navigation System (INS), the setup involves an Inertial Measurement Unit (IMU) that incorporates gyroscopes, accelerometers, and the Global Navigation Satellite System (GNSS).

During real-time navigation the INS estimates position and attitude based on current and past data only. However, the accuracy achieved in real-time is limited compared to what is possible through post-processing, where the entire survey data set is available.

An INS fitted with a datalogger enables the implementation of post-processing . This allows for unique capabilities, such as the ability to analyze data backward, commencing from the end and progressing back to the beginning of the file. By combining forward and backward processing, accuracy is significantly enhanced compared to real-time analysis. Post-processing also allows a comprehensive examination of the complete data set, leading to improved precision and reliability of navigation parameters.

Post-Processing – Corrections At the core of achieving precise GNSS-based positioning lies the implementation of correction solutions to enhance accuracy and integrity. Various correction types exist, but in scenarios where centimeter-level accuracy is imperative the two reliable options are Real-Time Kinematics (RTK) and Precise Point Positioning (PPP).

When exclusively working with real-time data, careful selection and configuration of the optimal correction method are essential prior to data acquisition. It is crucial to ensure that the correction data can be consistently obtained by the Inertial Navigation System (INS) .

In contrast, when engaging in post-processing, these constraints are lifted. The ability to select and apply correction data after acquisition not only enhances correction reliability by eliminating data gaps but also contributes to cost reduction. Moreover, post-processing allows for informed decision-making in correction selection and tuning based on a comprehensive understanding of the conditions during acquisition. Factors such as atmospheric conditions, which significantly influence processing quality and are challenging to predict in real-time, can be addressed more effectively during post-processing, leveraging full knowledge of the acquisition conditions.

Acquisitions far from a base station: VBS and IonoShield The distance between the base station and the rover drives the performance in RTK and PPK processing : the longer the distance, the lower the expected accuracy.

Qinertia leverages post-processing to offer two solutions to work around this issue: the Virtual Base Station (VBS) and IonoShield.

How does VBS work? VBS revolves around establishing a virtual network encompassing your project area, ensuring maximum, consistent, and robust position accuracy, especially when dealing with increased baseline distances affected by atmospheric disturbances.

In its operation, the VBS initially generates a map of atmospheric errors spanning the entire vehicle trajectory. These errors are then mitigated within the Qinertia PPK solution, ensuring a highly accurate navigation outcome, even in challenging conditions or during prolonged corridor surveys over considerable distances.

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How does IonoShield mode work? Ionoshield is an atmospheric error mitigation algorithm. It uses the observations on the base and on the rover to determine the errors introduced by the ionosphere and the troposphere. Ionoshield uses all available frequencies and constellations to estimate atmospheric errors and compensate them. An intelligent strategy minimizes the convergence time while the forward / backward / merge processing completes the process to target a zero-convergence time, even in challenging conditions.

Finally, the Ionoshield couples with the embedded RAIM algorithm to detect and exclude any faulty satellite due to ionospheric issues such as scintillation.

With this approach Ionoshield yields significant benefits:

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Post-Processing – Forward/Backward/Merge Algorithm The illustration highlights the effectiveness of the forward, backward, and merge processing in boosting data accuracy.

  In the forward phase, the position error grows rapidly until the GNSS signal returns after 60 seconds. Similarly, in the backward phase, the error increases until the GNSS signal is back at the 0-second mark. However, when we merge and smooth the data, the error is notably reduced, with the highest error occurring in the middle of the GNSS outage.

Why should geodetic conversion be considered in post-processing

Qinertia: Next-generation PPK software Qinertia stands out as SBG Systems' proprietary GNSS (Global Navigation Satellite System) and INS (Inertial Navigation System) post-processing software, delivering a comprehensive array of features to refine precise navigation data.

More about Qinertia PPK Software :

Book a free one-on-one online demo of Qinertia NOW![email protected] /bookings/s/07yts2TQ-kazBHJc4yf5VA2 

About SBG Systems: A leading supplier of innovative inertial sensors, SBG Systems manufactures and supports an extensive range of state-of-the-art inertial sensors, such as Inertial Measurement Units (IMU), Attitude and Heading Reference Systems (AHRS), and Inertial Navigation Systems with embedded GNSS (INS/GNSS).

This is a contributed article. Commercial UAV News taps the expertise of thought leaders throughout the drone industry to provide content to our site, enabling us to share a diverse set of ideas and perspectives with our audience.

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