References of "Kazmierski, Kamil"
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See detailAn Evaluaton of Real-Time Troposphere Products Based on mult-GNSS Precise Point Posi)oning
Ding, Wenwu; Teferle, Felix Norman UL; Kazmierski, Kamil et al

Scientific Conference (2017, February 21)

When employing observations from multiple Global Navigation Satellite System (GNSS) the performance of real-time (RT) GNSS meteorology can be improved. In this paper, we describe an operational RT system ... [more ▼]

When employing observations from multiple Global Navigation Satellite System (GNSS) the performance of real-time (RT) GNSS meteorology can be improved. In this paper, we describe an operational RT system for extracting zenith tropospheric delay (ZTD) using a modified version of the PPP-wizard. Multi-GNSS, including GPS, GLONASS and Galileo, observation streams are processed using a RT PPP strategy based on RT satellite orbit/clock products from CNES. A continuous experiment for 30 days is conducted, in which the RT observation streams of 20 globally distributed stations are processed. The initialization time and accuracy of the RT troposphere products using single/multi-system observations are evaluated. The effect of RT PPP ambiguity resolution is also evaluated. The results reveal that the RT troposphere products based on single system observations can fulfill the requirements of meteorological application, in which the GPS-only solution is better than the GLONASS-only solution in both initialization and accuracy. The performance can also be improved by applying RT PPP ambiguity resolution and utilizing multi-GNSS observations. Specifically, we notice that the ambiguity resolution is more effective in improving the accuracy, whereas the initialization process can be better accelerated by multi-GNSS observations. Combining all systems, RT troposphere products with an average accuracy of about 8 mm in ZTD can be achieved after an initialization process of approximately 9 minutes, which supports the application of multi-GNSS observations and ambiguity resolution for RT meteorological applications. [less ▲]

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See detailAn evaluation of real-time troposphere estimation based on GNSS Precise Point Positioning
Ding, Wenwu; Teferle, Felix Norman UL; Kazmierski, Kamil et al

in Journal of Geophysical Research: Atmospheres (2017), 122(5), 2779--2790

It is anticipated that the performance of real-time (RT) GNSS meteorology can be further improved by incorporating observations from multiple Global Navigation Satellite System (GNSS), including GPS ... [more ▼]

It is anticipated that the performance of real-time (RT) GNSS meteorology can be further improved by incorporating observations from multiple Global Navigation Satellite System (GNSS), including GPS, GLONASS, Galileo, and BeiDou. In this paper, an operational RT system for extracting zenith troposphere delay (ZTD) using a modified version of the Precise Point Positioning With Integer and Zero-difference Ambiguity Resolution Demonstrator (PPP-WIZARD) was established. GNSS, including GPS, GLONASS, and Galileo, observation streams were processed using RT Precise Point Positioning (PPP) strategy based on RT satellite orbit/clock products from the Centre National d'Etudes Spatiales. An experiment covering 30 days was conducted, in which the observation streams of 20 globally distributed stations were processed. The initialization time and accuracy of the RT troposphere results using single-system and multisystem observations were evaluated. The effect of PPP ambiguity resolution was also evaluated. Results reveal that RT troposphere estimates based on single-system observations can both be applied in weather nowcasting, in which the GPS-only solution is better than the GLONASS-only solution. The performance can also be improved by PPP ambiguity resolution and utilizing GNSS observations. Specifically, we notice that ambiguity resolution is more effective in improving the accuracy of ZTD, whereas the initialization process can be better accelerated by GNSS observations. Combining all techniques, the RT troposphere results with an average accuracy of about 8 mm in ZTD can be achieved after an initialization process of approximately 8.5 min, which demonstrates superior results for applying GNSS observations and ambiguity resolution for RT meteorological applications. [less ▲]

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See detailOptimum stochastic modeling for GNSS tropospheric delay estimation in real-time
Hadas, Tomasz; Teferle, Felix Norman UL; Kazmierski, Kamil et al

in GPS Solutions (2016)

In GNSS data processing, the station height, receiver clock and tropospheric delay (ZTD) are highly correlated to each other. Although the zenith hydrostatic delay of the troposphere can be provided with ... [more ▼]

In GNSS data processing, the station height, receiver clock and tropospheric delay (ZTD) are highly correlated to each other. Although the zenith hydrostatic delay of the troposphere can be provided with sufficient accuracy, zenith wet delay (ZWD) has to be estimated, which is usually done in a random walk process. Since ZWD temporal variation depends on the water vapor content in the atmosphere, it seems to be reasonable that ZWD constraints in GNSS processing should be geographically and/or time dependent. We propose to take benefit from numerical weather prediction models to define optimum random walk process noise. In the first approach, we used archived VMF1-G data to calculate a grid of yearly and monthly means of the difference of ZWD between two consecutive epochs divided by the root square of the time lapsed, which can be considered as a random walk process noise. Alternatively, we used the Global Forecast System model from National Centres for Environmental Prediction to calculate random walk process noise dynamically in real-time. We performed two representative experimental campaigns with 20 globally distributed International GNSS Service (IGS) stations and compared real-time ZTD estimates with the official ZTD product from the IGS. With both our approaches, we obtained an improvement of up to 10% in accuracy of the ZTD estimates compared to any uniformly fixed random walk process noise applied for all stations. [less ▲]

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See detailMulti-GNSS Benefits to Real-Time and Long-Term Monitoring Applications
Teferle, Felix Norman UL; Ding, Wenwu; Abraha, Kibrom Ebuy UL et al

Scientific Conference (2016, July 30)

The processing of observations from multiple Global Navigation Satellite Systems (GNSSs) has been shown to benefit high-precision applications on time scales from real-time (RT) to long-term monitoring ... [more ▼]

The processing of observations from multiple Global Navigation Satellite Systems (GNSSs) has been shown to benefit high-precision applications on time scales from real-time (RT) to long-term monitoring. While the improvements for RT applications have been widely documented and stem largely from the availability of additional observations, often with better satellite geometry, especially in obstructed environments, the improvements to long-term monitoring applications are less well understood. In this evaluation two distinct examples from recent studies carried out at the University of Luxembourg will be presented. Firstly, we will discuss RT estimates of Zenith Tropospheric Delay (ZTD) obtained using integer ambiguity fixed Precise Point Positioning (PPP) solutions based on GPS, GLONASS, Galileo and BDS observations. This study revealed that the largest improvement in the ZTD estimates stemmed from the additional GNSS observations to those of GPS. The fixing of integer ambiguities (GPS only) had less of an effect. Secondly, we will discuss long-term PPP solutions using GPS and GLONASS observations in combination with various satellite orbit and clock products from the International GNSS Service and its analysis centres. Here of particular interest are the constellation specific draconitic signals and the impact of signal obstructions on the long-term position time series. [less ▲]

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