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High-Precision RTK Positioning with Calibration-Free Tilt Compensation


To improve the applicability, productivity and user experience of high-precision RTK positioning, this paper presented the novel IMU-based tilt compensation approach of the Leica GS18 T smart antenna. When compared to the conventional magnetometer-based solutions, the proposed approach has the major advantages of being free from on-site calibrations, immune to magnetic disturbances and applicable at large tilt angles. Representative test results and benchmarking studies showed that using tilt compensation of the Leica GS18 T significantly increases productivity and enhances the positioning performance in difficult environments. These benefits are achieved by applying innovative technologies in satellite signal tracking and GNSS/INS integration. The main findings from the case studies are summarized as follows:

  •  The high-performance patch antenna in combination with ME7 enhances the low elevation angle tracking capabilities, with significantly larger SNR for L2 and L5.
  •  Under normal conditions with sufficient movements, the 3D attitude error is below 1.5 degrees. The GNSS and INS error components are largely uncorrelated and the total error budget of the pole tip position behaves according to the error propagation law.
  • Using tilt compensation, instantaneous measurement provides a similar accuracy level as static measurement, along with a favorable time-saving effect.
  • In comparison to conventional RTK with a vertical pole, using tilt compensation significantly increases productivity by up to 33% and considerably improves the near- building positioning performance regarding availability and accuracy.
  • On a parking lot with magnetic disturbances, the IMU-based tilt compensation produces more accurate positions and more realistic CQ than the magnetometer-based approach.
  • The proposed IMU-based tilt compensation is applicable at large tilt angles of more than 30 degrees, where a 3D positioning accuracy of 2 cm is still achievable.

By incorporating sensor heading into 3D visualization of the surroundings, the user can easily orientate himself in the survey environment, which improves productivity and user experience. With the Leica GS18 T, Leica Geosystems takes a new path and sets new standards for high- precision RTK positioning through sensor-fusion techniques.