Inertially Aided RTK for Robust and Precise Positioning

Short Description

Centimeter accurate positioning via GNSS would enable or boost a number of technologies being currently developed. This includes autonomously driving cars, augmented reality applications or unmanned aerial vehicles (UAV).

Whereas GNSS can provide this high accuracy via real-time-kinematic (RTK) positioning, RTK currently works only if there is a free line-of-sight between user and GNSS satellite. In urban areas, where most people live and the afore-mentioned applications are needed, the GNSS signal is often obstructed or reflected.

The availability of a RTK solution in urban areas is less than 50-70 % (depending on the type of the buildings), which renders RTK virtually useless for safety critical applications. For example, we can currently not imagine that an UAV flies autonomously in a city, e.g. for traffic monitoring.


This project targets to increase the RTK availability in urban areas to above 99 % by using GPS+Galileo L1/E1 and L5/E5a signals and by inertial aiding. A cost efficient microelectromechanical (MEMS) gyro and accelerometer (a so-called inertial measurement unit – IMU) will be used to detect cycle-slips within the GNSS carrier phase measurements. Cycle-slips are the main reason for the low RTK availability in urban areas.

A GPS/Galileo RTK module will be developed which is integrated with an ultra-tightly coupled GNSS/IMU receiver, to achieve continuous GNSS signal tracking even if obstructions are present. To mitigate multipath the principle of a synthetic antenna aperture will be used.

The Kalman filter will be extended based on IMU calibration campaigns and a parameter sensitivity analysis. This shall allow to use more cost efficient IMUs or to bridge longer GNSS signal outages (e.g. in an underpass). For verification, a ring-laser IMU based reference system will be integrated within a measurement vehicle. This allows establishing the ground truth with ~ 1 cm accuracy. The measurement vehicle will also carry competitive solutions used for comparisons. A fish-eye camera will allow identification of GNSS signal degradations and the data will be used to optimize the developed algorithms.

Expected Results

The primary benefit of the project is the improvement of GNSS receiver algorithms which will be sold or licensed. The market for those receivers is addressed in a generic technology oriented way, as done by competitors for this high-end technology. Scientific results in RTK or integrated navigation will be published for the sake of advancing the art of navigation. The expertise to conduct experiments and develop small-scale series products will be further enhanced.

Project Partners



Project partner

  • TU Graz

Contact Address

DI. Eva Bauer
Reininghausstraße 13a
A-8020 Vienna