New gxInteger algorithm adds RTK 2 cm accuracy to RT Post-process

Software Releases

November 22, 2013

RT Post-process from OxTS can now achieve 2 cm accuracy—making it the most competitively priced inertial and GNSS post-processing solution on the market. While many OxTS devices already output real-time RTK 2 cm measurements, it is not always possible for customers to set up a base-station or to send differential corrections to the host vehicle in survey applications. This is especially true where the area to be surveyed may be large or geographically challenging for radio signals, or where the use of multiple rovers makes a real-time solution too costly.

Post-processing data using a third-party application is a proven solution to the problem, but was not always cost-effective as the software represents a significant additional expenditure and adds extra steps to the workflow. The introduction of gxRTK integer processing directly within RT Post‑process solves both problems for OxTS customers; the post-processing is handled seamlessly by the same program that downloads the data and there is no need to purchase and maintain additional third-party software or multiple radios for receiving DGPS data.

The new gxInteger mode algorithm references CORS DGPS corrections contained in a RINEX file, RTCMV3 file or directly from the raw data file. It then applies corrections to the GPS data, and calculates an RTK integer position solution based on each signal’s carrier-phase in the same way as a real-time RTK solution. The corrected GPS data and inertial measurements are then referenced by the Kalman filter to provide a reliable and accurate position, orientation and velocity solution. Additionally, because the gxInteger solution is post-processed, it benefits from forwards/backwards processing, which is particularly useful for improving accuracy when conducting large-scale road network surveys.

Gx is a technology developed by OxTS specifically for GNSS-aided inertial navigation systems—and gxInteger is part of the same family. Gx algorithms ignore the navigation data calculated by GNSS receivers and instead calculate their own navigation measurements based on raw satellite data. They do this to stricter standards than normal, ensuring only high-quality GNSS measurements are referenced internally by the Kalman filter, improving the overall accuracy of the system.

As well as generating an RTK position solution, the new gxInteger algorithm also generates RTK-quality velocity and orientation measurements without the need for a base-station. Because the velocity measurements are derived by differencing the carrier phase measurements, the inherent errors are smaller than with velocity based instantaneous Doppler. This increased accuracy not only improves the velocity measurements, but also measurements such as slip angle. While the gxInteger position solution is not available on real-time systems, the gxInteger velocity solution is.

For more information on OxTS products or gxInteger post-processing, please contact your local OxTS representative.