WP2: GNSS-based distance measurement

The understanding of the influence of different sources of uncertainty to high‑accuracy GNSS‑based distance meters is thoroughly investigated in this project, making use of most modern technologies to isolate specific influences and to learn more about there impact. Ultimately, optimum calibration and application strategies will be developed, verified against the easier traceable optical measurement methods.

The "Bermuda triangle of entangled uncertainty influences of GNSS measurements ((c) by LUH)



1. A conceptual link between tropospheric effects and their impact on coordinate determination could be developed in WP2. This is an important step towards better quantification of the measurement uncertainty of GNSS-based distance metrology. A paper on this study has been published Opens external link in new windowhere.

Ultra-short common-clock baseline at PTB, Germany ((c) by PTB)

Investigating the influence of the first 50 cm. ((c) by UBO)

2. Common clock-GNSS baseline experiments are being performed for the first time to our knowledge in this project. This approach eliminates the necessity to determine the clock as free parameter from the satellite signals. This so‑called single-difference analysis will enable studies of other individual influences on the GNSS‑based distance measurement. Measurement campaigns with zero baseline, ultra-short (approx. 2 m), short (270 m) or long baselines (> 400 km) were performed.

3. A further challenge is the the influence of the first 50 cm of the antenna surrounding on the measurement result. Different configurations are being tested by experiments at the baseline of the University of the armed forces at Neubiberg, Germany. (First results are discussed here.)



New "revolver test field" for GNSS antenna calibration verification at Metsähovi, Finland ((c) by FGI)



4. A sophisticated field test for the validity of GNSS antenna calibration parameters has been developed on the basis of thorough simulations in the course of the project. The results were validated with non‑permanent setups. The most potential approach, the so‑called “revolver design” has been installed permanently at the Geodetic fundamental station in Metsähovi, Finland. The concept is discussed in more detail here.