Using external tropospheric corrections to improve GNSS positioning of hot-air balloon
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High accurate global navigation satellite systems (GNSS) require to correct a signal delay caused by the troposphere. The delay can be estimated along with other unknowns or introduced from external models. We assess the impact of the recently developed augmentation tropospheric model on real-time kinematic precise point positioning (PPP). The model is based on numerical weather forecast and thus reflects the actual state of weather conditions. Using the G-Nut/Geb software, we processed GNSS and meteorological data collected during the experiment using a hot-air balloon flying up to an altitude of 2000 m. We studied the impacts of random walk noise setting of zenith total delay (ZTD) on estimated parameters and the mutual correlations, the use of external tropospheric corrections, the use of data from a single or dual GNSS constellation and the use of Kalman filter and backward smoothing processing methods. We observed a significant negative correlation of the estimated rover height and ZTD which depends on constraining ZTD estimates. Such correlation caused a degraded performance of both parameters when estimated simultaneously, in particular for a single GNSS constellation. The impact of ZTD constraining reached up to 50-cm differences in the rover height. Introducing external tropospheric corrections improved the PPP solution regarding: (1) shortened convergence, (2) better overall robustness, particularly, in case of degraded satellite geometry, (3) less adjusted parameters with lower correlations. The numerical weather model-driven PPP resulted in 9–12- and 5–6-cm uncertainties in the rover altitude using the Kalman filter and the backward smoothing, respectively. Compared to standard PPP, it indicates better performance by a factor of 1–2 depending on the availability of GNSS constellations, the troposphere constraining and the processing strategy.
KeywordsGNSS Tropospheric corrections Zenith total delay Numerical weather forecast Precise point positioning Kinematic positioning
The experimental data collection, processing and tropospheric model enhancement have been supported by the ESA project DARTMA (EGEP-ID-89 06). The initial tropospheric model development has been supported by the ESA project Trop4LAS. We acknowledge the provision of data from operational weather forecasts run by the Institute of Computer Science of the Academy of Sciences, Czech Republic, within the DARTMA project.
- Dousa J, Vaclavovic P, Krc P, Elias M, Eben E, Resler J (2015a) NWM forecast monitoring with near real-time GNSS products, In: Proceedings of the 5th scientific Galileo colloquium, Braunschweig, Germany, October 27–29, 2015Google Scholar
- Dousa J, Elias M, Veerman H, van Leeuwen SS, Zelle H, de Haan S, Martellucci A, Perez RO (2015b) High accuracy tropospheric delay determination based on improved modelling and high resolution Numerical Weather Model. In: Proceedings ION GNSS 2015, Institute of Navigation, Tampa, Florida, USA, September 14–18, 3734-3744Google Scholar
- Schüler T, Hein G W, Eissfeller, B (2000) Towards an optimal strategy for GPS wet delay Kalman filtering. In: Proceedings of IAIN world congress 56th annual meeting of The Institute of NavigationGoogle Scholar
- Laurichesse D, Cerri L, Berthias J P, Mercier F (2013) Real time precise GPS constellation and clocks estimation by means of a Kalman filter. In: Proceedings ION GNSS 2013, Institute of Navigation, Nashville, Tennessee, USA, September 16–20, pp 1155–1163Google Scholar
- Mervart L, Weber G (2013) BKG Ntrip Client v2.9, software. https://igs.bkg.bund.de/ntrip/
- Michalakes J, Dudhia J, Gill D, Klemp J, Skamarock W (1998) Design of a next-generation regional weather research and forecast model. Towards Teracomputing. World Scientific, River Edge, pp 117–124Google Scholar
- RTCA (2006) Minimum operational performance standards for global positioning system/wide area augmentation system airborne equipment. RTCA publication DO-229DGoogle Scholar
- Saastamoinen J (1972) Atmospheric correction for the troposphere and stratosphere in radio ranging of satellites. In: The use of artificial satellites for geodesy. American Geophysical Union, Washington, DC doi: 10.1029/GM015p0247