scholarly journals Kinematic Zenith Tropospheric Delay Estimation with GNSS PPP in Mountainous Areas

Sensors ◽  
2021 ◽  
Vol 21 (17) ◽  
pp. 5709
Author(s):  
Paul Gratton ◽  
Simon Banville ◽  
Gérard Lachapelle ◽  
Kyle O’Keefe
Keyword(s):  
Ambiguity Resolution ◽  
Large Scale ◽  
Field Experiments ◽  
Integer Ambiguity Resolution ◽  
Global Navigation Satellite Systems ◽  
Integer Ambiguity ◽  
Tropospheric Delay ◽  
Mountainous Areas ◽  
Data Set ◽  
Zenith Tropospheric Delay

The use of global navigation satellite systems (GNSS) precise point positioning (PPP) to estimate zenith tropospheric delay (ZTD) profiles in kinematic vehicular mode in mountainous areas is investigated. Car-mounted multi-constellation GNSS receivers are employed. The Natural Resources Canada Canadian Spatial Reference System PPP (CSRS-PPP) online service that currently processes dual-frequency global positioning system (GPS) and Global’naya Navigatsionnaya Sputnikovaya Sistema (GLONASS) measurements and is now capable of GPS integer ambiguity resolution is used. An offline version that can process the above and Galileo measurements simultaneously, including Galileo integer ambiguity resolution is also tested to evaluate the advantage of three constellations. A multi-day static data set observed under open sky is first tested to determine performance under ideal conditions. Two long road profile tests conducted in kinematic mode are then analyzed to assess the capability of the approach. The challenges of ZTD kinematic profiling are numerous, namely shorter data sets, signal shading due to topography and forests of conifers along roads, and frequent losses of phase lock requiring numerous but not always successful integer ambiguity re-initialization. ZTD profiles are therefore often only available with float ambiguities, reducing system observability. Occasional total interruption of measurement availability results in profile discontinuities. CSRS-PPP outputs separately the zenith hydrostatic or dry delay (ZHD) and water vapour content or zenith wet delay (ZWD). The two delays are analyzed separately, with emphasis on the more unpredictable and highly variable ZWD, especially in mountainous areas. The estimated delays are compared with the Vienna Mapping Function 1 (VMF1), which proves to be highly effective to model the large-scale profile variations in the Canadian Rockies, the main contribution of GNSS PPP being the estimation of higher frequency ZWD components. Of the many conclusions drawn from the field experiments, it is estimated that kinematic profiles are generally determined with accuracy of 10 to 20 mm, depending on the signal harshness of the environment.

scholarly journals A Multi-Frequency Galileo PPP-RTK Convergence Analysis with an Emphasis on the Role of Frequency Spacing

2021 ◽  
Vol 13 (16) ◽  
pp. 3077
Author(s):  
Dimitrios Psychas ◽  
Peter J. G. Teunissen ◽  
Sandra Verhagen
Keyword(s):  
Ambiguity Resolution ◽  
Formal Analysis ◽  
Integer Ambiguity Resolution ◽  
Global Navigation Satellite Systems ◽  
Integer Ambiguity ◽  
Convergence Time ◽  
Frequency Separation ◽  
Dual Frequency ◽  
Single Receiver

The single-receiver integer ambiguity resolution-enabled variant of precise point positioning (PPP), namely PPP-RTK, has proven to be crucial in reducing the long convergence time of PPP solutions through the recovery of the integerness of the user-ambiguities. The proliferation of global navigation satellite systems (GNSS) supports various improvements in this regard through the availability of more satellites and frequencies. The increased availability of the Galileo E6 signal from GNSS receivers paves the way for speeding up integer ambiguity resolution, as more frequencies provide for a stronger model. In this contribution, the Galileo-based PPP-RTK ambiguity resolution and positioning convergence capabilities are studied and numerically demonstrated as a function of the number and spacing of frequencies, aiming to shed light on which frequencies should be used to obtain optimal performance. Through a formal analysis, we provide insight into the pivotal role of frequency separation in ambiguity resolution. Using real Galileo data on up to five frequencies and our estimated PPP-RTK corrections, representative kinematic user convergence results with partial ambiguity resolution are presented and discussed. Compared to the achieved performance of dual-frequency fixed solutions, it is found that the contribution of multi-frequency observations is significant and largely driven by frequency separation. When using all five available frequencies, it is shown that the kinematic user can achieve a sub-decimeter level convergence in 15.0 min (90% percentile). In our analysis, we also show to what extent the provision of the estimable satellite code biases as standard PPP-RTK corrections accelerates convergence. Finally, we numerically demonstrate that, when integrated with GPS, the kinematic user solution achieves convergence in 3.0 and 5.0 min on average and at 90%, respectively, in the presence of ionospheric delays, thereby indicating the single-receiver user’s fast-convergence capabilities.

scholarly journals Calibrating receiver-type-dependent wide-lane uncalibrated phase delay biases for PPP integer ambiguity resolution

2021 ◽  
Vol 95 (7) ◽  
Author(s):  
Bobin Cui ◽  
Pan Li ◽  
Jungang Wang ◽  
Maorong Ge ◽  
Harald Schuh
Keyword(s):  
Linear Combination ◽  
Ambiguity Resolution ◽  
Large Data ◽  
Phase Delay ◽  
Global Navigation Satellite Systems ◽  
Integer Ambiguity ◽  
Data Set ◽  
Uncalibrated Phase Delay ◽  
Ambiguity Fixing ◽  
Wide Lane

AbstractWide-lane (WL) uncalibrated phase delay (UPD) is usually derived from Melbourne–Wübbena (MW) linear combination and is a prerequisite in Global Navigation Satellite Systems (GNSS) precise point positioning (PPP) ambiguity resolution (AR). MW is a linear combination of pseudorange and phase, and the accuracy is limited by the larger pseudorange noise which is about one hundred times of the carrier phase noise. However, there exist inconsistent pseudorange biases which may have detrimental effect on the WL UPD estimation, and further degrade user-side ambiguity fixing. Currently, only the large part of pseudorange biases, e.g., the differential code bias (DCB), are available and corrected in PPP-AR, while the receiver-type-dependent biases have not yet been considered. Ignoring such kind of bias, which could be up to 20 cm, will cause the ambiguity fixing failure, or even worse, the incorrect ambiguity fixing. In this study, we demonstrate the receiver-type-dependent WL UPD biases and investigate their temporal and spatial stability, and further propose the method to precisely estimate these biases and apply the corrections to improve the user-side PPP-AR. Using a large data set of 1560 GNSS stations during a 30-day period, we demonstrate that the WL UPD deviations among different types of receivers can reach ± 0.3 cycles. It is also shown that such kind of deviations can be calibrated with a precision of about 0.03 cycles for all Global Positioning System (GPS) satellites. On the user side, ignoring the receiver-dependent UPD deviation can cause significant positioning error up to 10 cm. By correcting the deviations, the positioning performance can be improved by up to 50%, and the fixing rate can also be improved by 10%. This study demonstrates that for the precise and reliable PPP-AR, the receiver-dependent UPD deviations cannot be ignored and have to be handled.

scholarly journals An improved global zenith tropospheric delay model GZTD2 considering diurnal variations

2016 ◽  
Vol 23 (3) ◽  
pp. 127-136 ◽  
Author(s):  
Yibin Yao ◽  
Yufeng Hu ◽  
Chen Yu ◽  
Bao Zhang ◽  
Jianjian Guo
Keyword(s):  
Diurnal Variations ◽  
Global Navigation Satellite Systems ◽  
Atmospheric Parameter ◽  
Tropospheric Delay ◽  
Delay Model ◽  
Grid Data ◽  
Data Set ◽  
Average Bias ◽  
Global Average ◽  
Zenith Tropospheric Delay

Abstract. The zenith tropospheric delay (ZTD) is an important atmospheric parameter in the wide application of global navigation satellite systems (GNSS) technology in geoscience. Given that the temporal resolution of the current global zenith tropospheric delay model (GZTD) is only 24 h, an improved model, GZTD2, has been developed by taking the diurnal variations into consideration and modifying the model expansion function. The data set used to establish this model is the global ZTD grid data provided by Global Geodetic Observing System (GGOS) Atmosphere spanning from 2002 to 2009. We validated the proposed model with respect to ZTD grid data from GGOS Atmosphere, which was not involved in modeling, as well as International GNSS Service (IGS) tropospheric product. The obtained results of ZTD grid data show that the global average bias and root mean square (rms) for the GZTD2 model are 0.2 and 3.8 cm, respectively. The global average bias is comparable to that of the GZTD model, but the global average rms is improved by 3 mm. The bias and rms are far better than the EGNOS model and the UNB series models. The testing results from global IGS tropospheric product show the bias and rms (−0.3 and 3.9 cm) of the GZTD2 model are superior to that of GZTD (−0.3 and 4.2 cm), suggesting higher accuracy and reliability compared to the EGNOS model, as well as the UNB series models.

Applied Interval Based Integer Ambiguity Resolution

Navigation ◽  
2009 ◽  
Vol 56 (3) ◽  
pp. 205-219 ◽  
Author(s):  
E. VAN KAMPEN ◽  
E. DE WEERDT ◽  
Q.P. CHU ◽  
J.A. MULDER
Keyword(s):  
Ambiguity Resolution ◽  
Integer Ambiguity Resolution ◽  
Integer Ambiguity

scholarly journals An improved global zenith tropospheric delay model GZTD2 considering diurnal variations

2016 ◽  
Author(s):  
YiBin Yao ◽  
YuFeng Hu ◽  
Chen Yu ◽  
Bao Zhang ◽  
JianJian Guo
Keyword(s):  
Diurnal Variations ◽  
Atmospheric Parameter ◽  
Tropospheric Delay ◽  
Delay Model ◽  
Grid Data ◽  
International Gnss Service ◽  
Data Set ◽  
Average Bias ◽  
Global Average ◽  
Zenith Tropospheric Delay

Abstract. The zenith tropospheric delay (ZTD) is an important atmospheric parameter in the wide application of GNSS technology in geoscience. Given that the temporal resolution of the current Global Zenith Tropospheric Delay model (GZTD) is only 24 h, an improved model GZTD2 has been developed by taking the diurnal variations into consideration and modifying the model expansion function. The data set used to establish this model is the global ZTD grid data provided by Global Geodetic Observing System (GGOS) Atmosphere spanning from 2002 to 2009. We validated the proposed model with respect to ZTD grid data from GGOS Atmosphere, which was not involved in modeling, as well as International GNSS Service (IGS) tropospheric product. The obtained results of ZTD grid data show that the global average Bias and RMS for GZTD2 model are 0.2 cm and 3.8 cm respectively. The global average Bias is comparable to that of GZTD model, but the global average RMS is improved by 3 mm. The Bias and RMS are far better than EGNOS model and the UNB series models. The testing results from global IGS tropospheric product show the Bias and RMS (−0.3 cm and 3.9 cm) of GZTD2 model are superior to that of GZTD (−0.3 cm and 4.2 cm), suggesting higher accuracy and reliability compared to the EGNOS model, as well as the UNB series models.

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