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Using differential corrections with gx/ix in RT Post-process

Software Releases March 13, 2013

OxTS has updated RT Post-Process as part of the latest software release, meaning RINEX and RTCMv3 formatted base station data can now be applied in the new gx/ix mode. This update is particularly important for RT2500 and RT2502 users, as it is especially beneficial on these units. By applying differential correction data through the gx/ix processing algorithm, an RT2500 can now be post-processed to 90 cm CEP.


Gx/ix processing is the combination of two technologies (gx and ix) that allow RT Post-Process to work with raw satellite data in different ways depending on the quality and number of measurements available. When at least four valid GPS measurements are available, the system applies gx processing algorithms to calculate a GPS position and velocity, tailored to the needs of the Kalman filter, and ignores the solution computed by the GPS card. The ix mode, also known as single satellite aiding, is a technology that allows updating the navigation solution (Kalman Filter) without explicitly computing the GPS solution. The main advantage is that there is no constraint on the minimum number of satellite measurements. When less than four GPS measurements are available the system can still apply them using ix mode to reduce the system’s drift. The new technology achieves better integration between GPS and inertial data and maximises the use of GPS data.

In practice, the system initialises in gx mode and then arbitrates between gx and ix to optimise the trade-off between accuracy and efficiency, switching between ix mode when few satellites are visible and gx in good GPS conditions. The gx/ix mode does not invalidate the GPS card’s own positions which are logged, and therefore the standard processing can be selected in post-processing. Differential corrections are compatible with both ix and gx modes, as well as forwards-backwards processing. We currently support RTCMv3 differential corrections in real-time, and RINEX and RTCMv3 data files in post-processing.

If you would like more information on OxTS products or the latest software release, please contact OxTS or your regional OxTS representative.

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