Analysis of the Pseudorange Multipath Impact on Dual-Frequency Ionospheric Delay Correction in Compass System

2013 ◽  
pp. 355-365 ◽  
Author(s):  
Wei Zhao ◽  
Na Zhao ◽  
Haixing Zhao ◽  
Jinxian Zhao ◽  
Feng Xue ◽  
...  
Keyword(s):  
Ionospheric Delay ◽  
Dual Frequency ◽  
Delay Correction ◽  
Compass System

scholarly journals Long-term Performance Evaluation for Ionospheric Delay Correction of BeiDou Navigation Satellite System

2019 ◽  
Vol 131 ◽  
pp. 01075
Author(s):  
Chen Liu ◽  
Yi Jiang ◽  
Ye Chen ◽  
Ao Xu ◽  
Junpeng Li ◽  
...  
Keyword(s):  
Satellite System ◽  
Ionospheric Delay ◽  
Navigation Satellite ◽  
Dual Frequency ◽  
Correction Model ◽  
Beidou Navigation Satellite System ◽  
Correction Rate ◽  
Klobuchar Model ◽  
Delay Correction ◽  
Ionospheric Grid

Ionospheric delay is one of the main errors in the satellite navigation and positioning system. At present, ionospheric delay correction model and grid ionospheric information are provided to correct the error in BeiDou Navigation Satellite System (BDS). The ionospheric delay correction model is the Klobuchar model with 8 parameters at the geographic latitude for basic navigation. Grid ionospheric information is the ionospheric grid map covering China region for enhanced services. The dual-frequency pseudo-range combination data and ionospheric data from 2013 to 2018 have been used to make comprehensive assessments of the correction performance of BDS Klobuchar model and ionospheric grid information. The average correction rate of ionospheric grid information is about 85%, and the average correction rate of BDS Klobuchar model is about 73%. The correction accuracy of BDS Klobuchar model varies little, and the ionospheric grid information has a single-peak structure. The correction accuracy in summer and autumn is slightly higher than that in winter and spring. Changes in solar activity have a greater impact on BDS Klobuchar model correction bias. Ionospheric grid information owns relatively strong anti-disturbance ability, and BDS Klobuchar model also has a definite anti-disturbance capability compared with the GPS Klobuchar model.

scholarly journals Evaluation of Seasonal Variability of First-order Ionospheric Delay Correction at L5 and S1 Frequencies Using Dual-frequency Navic System

2021 ◽  
Author(s):  
Sharat chandra Bhardwaj ◽  
Anurag Vidyarthi ◽  
Bhajan Singh Jassal ◽  
Ashish kumar Shukla
Keyword(s):  
Seasonal Variability ◽  
Ionospheric Delay ◽  
Electron Content ◽  
Dual Frequency ◽  
Satellite Constellations ◽  
Total Electron ◽  
First Order ◽  
Seasonal Characteristics ◽  
Geosynchronous Satellites ◽  
Delay Correction

Abstract For the precise positioning application it is important to determine and eliminate the positioning error introduced by various sources such as the ionosphere. To develop a standalone precise navigation system, India has launched the seven satellite constellations of NavIC (Navigation with Indian Constellation) system to provide precision positioning over India and surrounded landmass. Since the ionospheric delay depends on the frequency of the satellite signal and NavIC systems work at different frequencies (L5 and S1) than GPS systems (L1 and L2), it is not possible to use the GPS data-driven study for NavIC based location calculations directly. Thus there is a need for a specialized ionospheric study for NavIC systems. In addition, the ionospheric delay is directly proportional to Slant Total Electron Content (STEC) which is dependent upon diurnal and seasonal solar activity. To achieve accurate positioning facilities, there is also a need for evaluation for seasonal variability of ionospheric delay correction for NavIC receivers. This paper deals with the STEC estimation; its smoothing, and removal of instrumental biases from STEC. The determined true STEC has been used to determine first-order ionospheric delay at L5 and S1 frequencies. The delay at S1 has been found less (2 to 7m) as compared to L5 (10 to 30m). Furthermore, the seasonal variability of ionospheric delay has been analyzed using about 19 months of data (from June 2017 to December 2018) and found that the ionospheric delay follows unique seasonal characteristics which can be utilized for delay modeling. It has been also observed that the geostationary satellites of the NavIC system are more appropriate than geosynchronous satellites for ionospheric related studies.

scholarly journals Improving the Stochastic Model of Ionospheric Delays for BDS Long-Range Real-Time Kinematic Positioning

2021 ◽  
Vol 13 (14) ◽  
pp. 2739
Author(s):  
Huizhong Zhu ◽  
Jun Li ◽  
Longjiang Tang ◽  
Maorong Ge ◽  
Aigong Xu
Keyword(s):  
Real Time ◽  
Long Range ◽  
Ionospheric Delay ◽  
Time Interval ◽  
Short Time Interval ◽  
Dual Frequency ◽  
Triple Frequency ◽  
Ambiguity Fixing ◽  
Power Spectral ◽  
Observation Noise

Although ionosphere-free (IF) combination is usually employed in long-range precise positioning, in order to employ the knowledge of the spatiotemporal ionospheric delays variations and avoid the difficulty in choosing the IF combinations in case of triple-frequency data processing, using uncombined observations with proper ionospheric constraints is more beneficial. Yet, determining the appropriate power spectral density (PSD) of ionospheric delays is one of the most important issues in the uncombined processing, as the empirical methods cannot consider the actual ionosphere activities. The ionospheric delays derived from actual dual-frequency phase observations contain not only the real-time ionospheric delays variations, but also the observation noise which could be much larger than ionospheric delays changes over a very short time interval, so that the statistics of the ionospheric delays cannot be retrieved properly. Fortunately, the ionospheric delays variations and the observation noise behave in different ways, i.e., can be represented by random-walk and white noise process, respectively, so that they can be separated statistically. In this paper, we proposed an approach to determine the PSD of ionospheric delays for each satellite in real-time by denoising the ionospheric delay observations. Based on the relationship between the PSD, observation noise and the ionospheric observations, several aspects impacting the PSD calculation are investigated numerically and the optimal values are suggested. The proposed approach with the suggested optimal parameters is applied to the processing of three long-range baselines of 103 km, 175 km and 200 km with triple-frequency BDS data in both static and kinematic mode. The improvement in the first ambiguity fixing time (FAFT), the positioning accuracy and the estimated ionospheric delays are analysed and compared with that using empirical PSD. The results show that the FAFT can be shortened by at least 8% compared with using a unique empirical PSD for all satellites although it is even fine-tuned according to the actual observations and improved by 34% compared with that using PSD derived from ionospheric delay observations without denoising. Finally, the positioning performance of BDS three-frequency observations shows that the averaged FAFT is 226 s and 270 s, and the positioning accuracies after ambiguity fixing are 1 cm, 1 cm and 3 cm in the East, North and Up directions for static and 3 cm, 3 cm and 6 cm for kinematic mode, respectively.

scholarly journals Assessing the quality of ionospheric models through GNSS positioning error: methodology and results

GPS Solutions ◽  
2019 ◽  
Vol 24 (1) ◽  
Author(s):  
Adrià Rovira-Garcia ◽  
Deimos Ibáñez-Segura ◽  
Raul Orús-Perez ◽  
José Miguel Juan ◽  
Jaume Sanz ◽  
...  
Keyword(s):  
Satellite System ◽  
Ionospheric Delay ◽  
Single Frequency ◽  
Positioning Error ◽  
Dual Frequency ◽  
Error Sources ◽  
Ionospheric Models ◽  
Evaluation Metric ◽  
Global Navigation Satellite

Abstract Single-frequency users of the global navigation satellite system (GNSS) must correct for the ionospheric delay. These corrections are available from global ionospheric models (GIMs). Therefore, the accuracy of the GIM is important because the unmodeled or incorrectly part of ionospheric delay contributes to the positioning error of GNSS-based positioning. However, the positioning error of receivers located at known coordinates can be used to infer the accuracy of GIMs in a simple manner. This is why assessment of GIMs by means of the position domain is often used as an alternative to assessments in the ionospheric delay domain. The latter method requires accurate reference ionospheric values obtained from a network solution and complex geodetic modeling. However, evaluations using the positioning error method present several difficulties, as evidenced in recent works, that can lead to inconsistent results compared to the tests using the ionospheric delay domain. We analyze the reasons why such inconsistencies occur, applying both methodologies. We have computed the position of 34 permanent stations for the entire year of 2014 within the last Solar Maximum. The positioning tests have been done using code pseudoranges and carrier-phase leveled (CCL) measurements. We identify the error sources that make it difficult to distinguish the part of the positioning error that is attributable to the ionospheric correction: the measurement noise, pseudorange multipath, evaluation metric, and outliers. Once these error sources are considered, we obtain equivalent results to those found in the ionospheric delay domain assessments. Accurate GIMs can provide single-frequency navigation positioning at the decimeter level using CCL measurements and better positions than those obtained using the dual-frequency ionospheric-free combination of pseudoranges. Finally, some recommendations are provided for further studies of ionospheric models using the position domain method.

scholarly journals On Global Ionospheric Maps based winter-time GPS ionospheric delay with reference to the Klobuchar model

Pomorstvo ◽  
2019 ◽  
Vol 33 (2) ◽  
pp. 210-221
Author(s):  
David Brčić ◽  
Renato Filjar ◽  
Serdjo Kos ◽  
Marko Valčić
Keyword(s):  
Ionospheric Delay ◽  
Single Frequency ◽  
Electron Content ◽  
Ground Truth Data ◽  
Local Pattern ◽  
Satellite Positioning ◽  
Klobuchar Model ◽  
Global Ionospheric Maps ◽  
Winter Time ◽  
Delay Correction

Modelling of the ionospheric Total Electron Content (TEC) represents a challenging and demanding task in Global Navigation Satellite Systems (GNSS) positioning performance. In terms of satellite Positioning, Navigation and Timing (PNT), TEC represents a significant cause of the satellite signal ionospheric delay. There are several approaches to TEC estimation. The Standard (Klobuchar) ionospheric delay correction model is the most common model for Global Positioning System (GPS) single-frequency (L1) receivers. The development of International GNSS Service (IGS) Global Ionospheric Maps (GIM) has enabled the insight into global TEC dynamics. GIM analyses in the Northern Adriatic area have shown that, under specific conditions, local ionospheric delay patterns differ from the one defined in the Klobuchar model. This has been the motivation for the presented research, with the aim to develop a rudimentary model of the TEC estimation, with emphasis on areas where ground truth data are not available. The local pattern of the ionospheric delay has been modelled with wave functions based on the similarity of waveforms, considering diurnal differences in TEC behavior from defined TEC patterns. The model represents a spatiotemporal winter-time ionospheric delay correction with the Klobuchar model as a basis. The evaluation results have shown accurate approximation of the local pattern of the ionospheric delay. The model was verified in the same seasonal period in 2007, revealing it successfulness under pre-defined conditions. The presented approach represents a basis for the further work on the local ionospheric delay modelling, considering local ionospheric and space weather conditions, thus improving the satellite positioning performance for single-frequency GNSS receivers.

scholarly journals Regiomontan: A Regional High Precision Ionosphere Delay Model and Its Application in Precise Point Positioning

Sensors ◽  
2020 ◽  
Vol 20 (10) ◽  
pp. 2845
Author(s):  
Janina Boisits ◽  
Marcus Glaner ◽  
Robert Weber
Keyword(s):  
Precise Point Positioning ◽  
Ionospheric Delay ◽  
Single Frequency ◽  
External Information ◽  
Delay Model ◽  
Dual Frequency ◽  
Propagation Delays ◽  
Point Positioning ◽  
The Difference ◽  
High Level

Propagation delays of GNSS signals caused by the ionosphere can range up to several meters in zenith direction and need to be corrected. Geodetic receivers observing at two or more frequencies allow the mitigation of the ionospheric effects by forming linear combinations. However, single frequency users depend on external information. The ionosphere delay model Regiomontan developed at TU Wien is a regional ionospheric delay model providing high accuracy information with a latency of only a few hours. The model is based on dual-frequency phase observations of a regional network operated by EPOSA (Echtzeit Positionierung Austria) and partners. The corrections cover a geographical extent for receiver positions within Austria and are provided in the standardized IONEX format. The performance of Regiomontan as well as its application in Precise Point Positioning (PPP) were tested with our in-house PPP software raPPPid using the so-called uncombined model with ionospheric constraint. Various tests, e.g., analyzing the coordinate convergence behavior or the difference between estimated and modeled ionospheric delay, proving the high level of accuracy provided with Regiomontan. We conclude that Regiomontan performs at a similar level of accuracy as IGS final TEC maps, but with explicitly reduced latency.

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