Project Settings

The project settings dialog box lets you review and change all the configurations that could affect the processing such as the GNSS antenna lever arms, the motion profile etc. You can open it at any time from the main tool bar icon or from the Project→Configuration main menu.

Processing

Motion Profiles

The first part of this panel is used to select the motion profile to use for processing. The motion profile affects how the GNSS and INS fusion algorithms behave. For example, for car applications, Qinertia can make some assumptions about the vehicle dynamics to optimize the accuracy especially in harsh GNSS environments.

The motion profile selection also affects which aiding (GNSS, DVL, Odometer) can be used as well as some options availability. It also defines which time series and displays are available. For example, track slip angle plot is only available if you have selected a ground motion profile such as automotive. It's the same for heave time series plot that is only available if you have selected a marine motion profile.

Processing options

Theses options affect the overall processing options.

• Force Single Pass: By default, for INS processing modes, Qinertia process the log three times to improve the solution accuracy and remove convergence effects. Thanks to this technique, the beginning and end of the log has the same accuracy as the rest of the mission. However, if you have long logs and are not interested in the beginning and the end of the mission can check this option to reduce processing time.
• Execute a dedicated estimation processing: Select this option to enable mechanical installation parameters estimation mode. This mode focuses on lever arm estimation and not on INS solution itself. Please read the dedicated Lever Arm Estimation page for more details.
• Enable Enhanced Altitude: This option is only available for marine applications. The heave data is used in the INS solution to improve altitude drift during GNSS outages. It is recommended if you are doing surveys under large bridges or you have long GNSS outages.
• Constellations Selection: You can disable some constellations in the GNSS or INS tightly coupled solutions. This can be helpful for troubleshooting purposes but you should normally just let all constellations enabled.

Processing modes

This panel simply displays all the processing modes that are available based on your current project configuration, imported data and Qinertia license.

IMU Model

You can select the IMU model to use in the processing as well as the IMU reference point of measurements.

IMU Selection

When you import a project, Qinertia will try to parse INS settings if they are available to pickup the correct IMU Model automatically. It's the case if you import an acquisition from a NAVSIGHT unit for example. Qinertia will automatically read from the imported files the IMU model that was connected to the NAVSIGHT processing unit and select it.

However, if the imported data don't store this parameter or if you create an empty project, you will have to manually select the right IMU model. This is the case, for example, if you would like to process third party IMU/INS and you should refer to the list of available IMU Models.

The IMU model not only tune the error model but also defines some mechanical settings such as the list of available IMU reference points.

IMU Reference Point

The IMU reference point defines where all the lever arms have to be measured from as well as where the INS solution has to be computed. SBG Systems INS products define several reference points to ease the INS installation and swap if case of maintenance. All SBG Systems INS have several reference points defined except for ELLIPSE and OEM products. On the other hand, most third party IMUs don't have reference points.

For example, a EKINOX IMU offers three reference points:

• Bare IMU: doesn't apply any offset so the INS solution is computed at the IMU physical measurement point so are measured the lever arms. You thus have to look in the documentation where this IMU physical point is located from the IMU/INS enclosure and do the math by yourselves.
• Cover Target: The IMU reference point is relocated at the enclosure top cover target. This target is precisely engraved using laser marking and can be easily used with total stations to get very accurate lever arms measurements.
• Base Plate Hole: The IMU reference point is relocated at the base mounting plate alignment hole. This is very interesting if you have measured the lever arms from CAD models for instance.

You can also enter a custom X,Y,Z reference point. This is very helpful if the IMU/INS is integrated within an other system/enclosure. The end users will not have to bother applying lever arms offset himself.

Reference Point Conventions

The IMU reference point has to be expressed in the IMU body frame and not in the vehicle or North, East, Down navigation frame. Qinertia can then nicely handle IMU rotations this way.

IMU installation

This panel is used to define how the IMU is installed within the vehicle. It exposes two settings, the IMU alignment and the primary lever arm. You can read the Accounting for misalignment page to get background information.

Primary Lever Arm

The primary lever arm is used to enter the offset from the IMU to the vehicle center of rotations. This is used by the INS filter for some motion profiles such as ground vehicles to correctly apply the lateral motion constraints. This parameter is also used for ship motion computations to improve the heave filter stability.

Automotive Applications

If no odometer is setup, the INS filter will use the primary lever arm to correctly apply lateral motion constraints otherwise the odometer lever arm is used.

Qinertia also automatically refines the entered lever arm to improve the INS accuracy during GNSS outages or in harsh GNSS conditions. Indeed, even an error of 1 cm on this lever arm can decrease the INS accuracy.

IMU Alignment

To work correctly, an INS has to be carefully installed and aligned within a vehicle. The INS filter expects to have the IMU X axis pointing forward, the Y axis pointing right and the Z axis pointing down. If the IMU can't be mechanically aligned to the vehicle frame, you can enter the misalignment between the IMU and the vehicle in Qinertia.

Qinertia offers a nice and easy control to input this misalignment using a rough and then a fine misalignment. You should first enter the rough misalignment to define how axis are oriented and then you can enter the residual fine misalignment as roll, pitch and yaw angles.

For example, if you install the INS with the X axis pointing backward instead of forward, you simply have to select in the rough alignment settings, Backward option for the X axis and Left for the Y axis.

Origin IMU alignment

This is an advanced settings used to handle nicely all IMU/INS manufacturers conventions. Some IMU manufacturers output IMU data that is never re-aligned whatever the INS configuration is and others such as SBG Systems output IMU data that has been re-aligned to the vehicle frame according to the user configuration.

Qinertia has to know if the IMU data has been already re-aligned or not and if so which alignment has been applied. This is mandatory so Qinertia doesn't re-apply the same alignment twice.

An other more complex situation is IMU data that has been re-aligned with wrong settings during the acquisition and the user would like to fix this in Qinertia. Qinertia has to know which alignment has been applied on the IMU data to remove it to then apply the correct alignment entered in Qinertia.

This alignment is called the origin IMU alignment and can be manually entered if Qinertia was not able to read it from the imported data.

The origin IMU alignment setting only makes sense for IMU/INS manufacturers that re-align the IMU data. Please contact SBG Systems support@sbg-systems.com team for more information.

Output Frames

Qinertia can output the INS solutions at up to three user defined output frames. For each output frame, you can enter a rotation to apply on the INS solution as well as a lever arm to relocate the INS solution. This feature is very helpful to ease integration with other sensors and devices such as Lidar or cameras as you can export an INS solution in their frame directly.

Output frames have no impact on the processing itself and are only used when data is exported by Qinertia.

Once you have defined an output frame, don't forget to select it when you export your project.

GNSS aiding

This panel is used to configure the GNSS aiding such as the lever arms, antenna, etc. You can read the GNSS antenna installation article to get more details and some recommendations.

To be more specific, this panel is used to setup the configuration for three aiding sources:

• GNSS RAW: Used for all tightly coupled INS salutations and GNSS only computations.
• GNSS PVT: Used for INS reprocessing modes
• GNSS Dual Antenna: Used for all INS processing modes.

Each aiding can come from a different GNSS receiver or device so it is possible to have different configurations and lever arms for each input. If Qinertia detects that RAW, PVT and True Heading data is not coming from the same device, it adds an Advanced button so you can configure each input individually.

In this documentation, we will however, only describe the standard case where the same GNSS provides the PVT trajectory, RAW data and true heading measurements.

Please find below the explanation of each setting:

GNSS Antenna

Please take attention to the selected GNSS antenna and associated settings to obtain the right absolute altitude output.

Odometer aiding

This panel is used to setup the odometer also called DMI (Distance Measurement Instrument) aiding. It is only available if you have selected a ground vehicle motion profile and have imported odometer data.

Please find below the description of each setting:

DVL aiding

You can setup the Doppler Velocity Logger (DVL) aiding. The DVL is manly used to provide a 3D water layer and bottom velocity to improve INS robustness and accuracy under very harsh conditions and long outages. This panel is only available if you have selected a marine motion profile and have imported DVL data.

Please find below the description of each setting:

Export/Reports Output

In Qinertia, the export and report generation steps are part of the project settings. This is very useful to support project publishing that automatically execute all configured export jobs as well as generate all enabled reports. This is also interesting to enable, project creation from project template that per-configure also export and report generation steps.

You can select which export profiles and which report templates have to be generated during project publication. You can also decide if data export and report generation should be triggered automatically when the processing is done.

Finally, from this panel, you can also access the Export Profile and Report Template Manager dialog boxes to create/edit/manage export profiles and report templates.