Mitigating Large Position Errors in INS/MRU/WS with GNSS Receiver

Posted by Will Dillingham on Aug 19, 2020 2:29:16 PM

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Purpose: The purpose of this Knowledge Base article to is outline a few commonly seen issues and fixes that surround large GNSS position errors seen internationally. It is important to note that these issues are not at the fault of Inertial Labs products, but satellite line of sight issues, and satellite correction services.

Last Updated: March 2020

 

Recommendations to take if end-user is seeing consistent GNSS position errors.

  1. Make sure that the INS is configured to receive regular updates for GNSS position. In many cases when the INS (or MRU/WS) is configured to receive GNSS position updates at 1 Hz the update rate is too seldom for ideal INS filter convergence. It is recommend to have the INS configured to receive GNSS position updates at 20 Hz, or at a minimum, 10 Hz.

  2. Ensure that you have a reliable amount of satellites that the INS is receiving updates from. In a recent example from a customer of Inertial Labs, the end-user was using only GPS L1 while driving and often only having access to less than 4 satellites due to being in a remote position on the globe. At a minimum, any receiver needs at least 4 satellites to be able to correctly calculate position, velocity and time. With that being said Inertial Labs always recommends using multi-constellation updates (at least GPS+GLONASS).

  3. Inertial Labs by default configures products with GNSS receivers to receive SBAS GNSS corrections when shipped to customers. Internationally, it has been brought to the attention of the Inertial Labs engineering team that SBAS correction services are not working ideally in many parts of the globe. Receivers may be getting corrections that are in fact worse than the solution received without SBAS enabled. As of right now SBAS GNSS corrections are working well in the United States, and in Europe. In regions like the Middle East where The European Geostationary Navigation Overlay Service (EGNOS) are providing SBAS updates, there have been reports of position errors of 100 meters. Inertial Labs as a result recommends that users turn off correction services until they know what correction services can be trusted in the area where the unit will be operating.

 

When users mitigate risk by taking into effect the recommendations above, the INS (or MRU/WS) indeed shows the expected performance even though GNSS reliability is still affected by urban environments.

However, if the user should ever have any questions or concerns on the reliability of there solution, please do not hesitate to reach out to our Customer Support Team. We would be more than happy to help you!

 

Topics: MRU, INS, receiver, Error, Position, EGNOS, WS, SBAS, Correction


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