scholarly journals Case study on complex sporadic E layers observed by GPS radio occultations

2014 ◽  
Vol 7 (9) ◽  
pp. 9203-9236 ◽  
Author(s):  
X. Yue ◽  
W. S. Schreiner ◽  
Z. Zeng ◽  
Y.-H. Kuo ◽  
X. Xue
Keyword(s):  
Satellite System ◽  
Time Interval ◽  
Long Distance ◽  
Shear Theory ◽  
Long Time ◽  
Distance Communication ◽  
Statistical Studies ◽  
Sporadic E ◽  
Global Navigation Satellite ◽  
Event Based

Abstract. The occurrence of sporadic E (Es) layer has been a hot scientific topic for a long time. Global Navigation Satellite System (GNSS) based Radio Occultation (RO) has been proven a powerful technique on detecting the global Es layers. In this paper, we focus on some cases of complex Es layers based on the RO data from multiple missions processed in UCAR/CDAAC. We first show some examples of multiple Es layers occurred in one RO event. Based on the evaluations between co-located simultaneous RO events and between RO and Lidar observations, it could be concluded that some of these do manifest the multiple Es layered structures. We then show a case of the occurrence of Es in a broad region during a certain time interval. The result is then validated by the independent ionosondes observations. These complex Es structures could be understood well by the popular wind shear theory. We could map the global Es occurrence routinely in the near future given that more RO data will be available. Further statistical studies will enhance our understanding on the Es mechanism. The specification on Es should benefit both the Es based long distance communication and accurate neutral RO retrievals.

scholarly journals Case study on complex sporadic E layers observed by GPS radio occultations

2015 ◽  
Vol 8 (1) ◽  
pp. 225-236 ◽  
Author(s):  
X. Yue ◽  
W. S. Schreiner ◽  
Z. Zeng ◽  
Y.-H. Kuo ◽  
X. Xue
Keyword(s):  
Satellite System ◽  
Time Interval ◽  
Long Distance ◽  
Shear Theory ◽  
Layer Structures ◽  
Long Time ◽  
Distance Communication ◽  
Sporadic E ◽  
Global Navigation Satellite ◽  
Event Based

Abstract. The occurrence of sporadic E (Es) layers has been a hot scientific topic for a long time. The GNSS (global navigation satellite system)-based radio occultation (RO) has proven to be a powerful technique for detecting the global Es layers. In this paper, we focus on some cases of complex Es layers based on the RO data from multiple missions processed in UCAR/CDAAC (University Corporation for Atmospheric Research (UCAR) the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Data Analysis and Archive Center (CDAAC)). We first show some examples of multiple Es layers occurred in one RO event. Based on the evaluations between colocated simultaneous RO events and between RO and lidar observations, it could be concluded that some of these do manifest the multiple Es layer structures. We then show a case of the occurrence of Es in a broad region during a certain time interval. The result is then validated by independent ionosondes observations. It is possible to explain these complex Es structures using the popular wind shear theory. We could map the global Es occurrence routinely in the near future, given that more RO data will be available. Further statistical studies will enhance our understanding of the Es mechanism. The understanding of Es should benefit both Es-based long-distance communication and accurate neutral RO retrievals.

scholarly journals Investigation of method of elimination of interference situation effect on GPS navigation receiver operation by smoothing of pseudorange measurements by pseudophase increment

2020 ◽  
pp. 46-53
Author(s):  
V. Y. Vovasov ◽  
D. A. Sukharev
Keyword(s):  
High Precision ◽  
Experimental Studies ◽  
Satellite System ◽  
Mobile Object ◽  
Time Interval ◽  
Urgent Task ◽  
Long Time ◽  
The Difference ◽  
Navigation Signals ◽  
Global Navigation Satellite

The wide application of high-precision GNSS (global navigation satellite system) positioning technologies for unmanned mobile object management requires the acquisition of solutions with subdecimeter accuracy and the reduction of the convergence period to such accuracy from the beginning of measurements to 20–25 minutes. Unfortunately, the accuracy of the obtained navigation solutions and the time of convergence to high-precision solutions are influenced by re-reflection of GNSS signals from the ground, buildings and structures, as well as interference from different sources of radio emissions of the urban environment. Therefore, it is an urgent task to implement methods of eliminating the influence of the interference situation on the operation of the navigation receiver of GNSS signals and investigating their effectiveness. The paper considers the results of investigation of the method of elimination of interference situation effect on GPS signal navigation receiver operation using smoothing of raw pseudorange measurements by pseudophase increment. Justification of the difference of measurement of pseudo-range by carrier phase and pseudo-range by code is given as a criterion of efficiency of estimation of interference situation influence in the area of navigation signals reception. As a result of the analysis of experimental studies, it has been shown that using the described method, starting from 900 seconds, the values of the smoothed parameter do not deviate from the averaged measurements over a long time interval by more than 0.1 meters, which indicates the efficiency of the method of smoothing by phase increments and is potentially promising for highly accurate measurements.

scholarly journals Derivation of global ionospheric Sporadic E critical frequency ( f o Es) data from the amplitude variations in GPS/GNSS radio occultations

2020 ◽  
Vol 7 (7) ◽  
pp. 200320 ◽  
Author(s):  
Bingkun Yu ◽  
Christopher J. Scott ◽  
Xianghui Xue ◽  
Xinan Yue ◽  
Xiankang Dou
Keyword(s):  
Critical Frequency ◽  
Detection Threshold ◽  
Low Frequency ◽  
Satellite System ◽  
Global Scale ◽  
Satellite Mission ◽  
Frequency Detection ◽  
Sporadic E ◽  
The Uk ◽  
Global Navigation Satellite

The ionospheric sporadic E (Es) layer has a significant impact on the global positioning system (GPS)/global navigation satellite system (GNSS) signals. These influences on the GPS/GNSS signals can also be used to study the occurrence and characteristics of the Es layer on a global scale. In this paper, 5.8 million radio occultation (RO) profiles from the FORMOSAT-3/COSMIC satellite mission and ground-based observations of Es layers recorded by 25 ionospheric monitoring stations and held at the UK Solar System Data Centre at the Rutherford Appleton Laboratory and the Chinese Meridian Project were used to derive the hourly Es critical frequency ( f o Es) data. The global distribution of f o Es with a high spatial resolution shows a strong seasonal variation in f o Es with a summer maximum exceeding 4.0 MHz and a winter minimum between 2.0 and 2.5 MHz. The GPS/GNSS RO technique is an important tool that can provide global estimates of Es layers, augmenting the limited coverage and low-frequency detection threshold of ground-based instruments. Attention should be paid to small f o Es values from ionosondes near the instrumental detection limits corresponding to minimum frequencies in the range 1.28–1.60 MHz.

scholarly journals Experimental Evaluation of the Impact of Different Types of Jamming Signals on Commercial GNSS Receivers

2020 ◽  
Vol 10 (12) ◽  
pp. 4240 ◽  
Author(s):  
Haidy Elghamrawy ◽  
Malek Karaim ◽  
Mohamed Tamazin ◽  
Aboelmaged Noureldin
Keyword(s):  
Satellite System ◽  
Signal Interference ◽  
Interference Signal ◽  
Long Distance ◽  
Wideband Signals ◽  
Global Positioning ◽  
Gnss Receivers ◽  
Propagation Medium ◽  
Global Navigation Satellite ◽  
The Impact

The received global navigation satellite system (GNSS) signal has a very low power due to traveling a very long distance and to the nature of the signal’s propagation medium. Thus, GNSS signals are easily susceptible to signal interference. Signal interference can cause severe degradation or interruption in GNSS position, navigation, and timing (PNT) services which could be very critical, especially in safety-critical applications. The objective of this paper is to evaluate the impact of the presence of jamming signals on a high-end GNSS receiver and investigate the benefits of using a multi-constellation system under such circumstances. Several jamming signals are considered in this research, including narrowband and wideband signals that are located on GPS L1 or GLONASS L1 frequency bands. Quasi-real dynamic trajectories are generated using the Spirent™ GSS6700 GNSS signal simulator combined with an interference signal generator through a Spirent™ GSS8366 unit. The performance evaluation was carried out using several evaluation metrics, including signal power degradation, navigation solution availability, dilution of precision (DOP), and positioning accuracy. The multi-constellation system presented better performance over the global positioning system (GPS)-only constellation in most cases. Moreover, jamming the GPS band caused more critical effects than jamming the GLONASS band.

scholarly journals Sparse GLONASS Signal Acquisition Based on Compressive Sensing and Multiple Measurement Vectors

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Guodong He ◽  
Maozhong Song ◽  
Shanshan Zhang ◽  
Peng Song ◽  
Xinwen Shu
Keyword(s):  
Compressive Sensing ◽  
Satellite System ◽  
New Method ◽  
Signal Acquisition ◽  
Multiple Measurement ◽  
Multiple Measurement Vectors ◽  
Navigation Data ◽  
Long Time ◽  
Global Navigation Satellite ◽  
Sparse Features

A sparse global navigation satellite system (GLONASS) signal acquisition method based on compressive sensing and multiple measurement vectors is proposed. The nonsparse GLONASS signal can be represented sparsely on our proposed dictionary which is designed based on the signal feature. Then, the GLONASS signal is sensed by a normalized orthogonal random matrix and acquired by the improved multiple measurement vectors acquisition algorithm. There are 10 cycles of pseudorandom codes in a navigation message, and these 10 pseudorandom codes have the same row sparse structure. So, the acquisition probability can be raised by row sparse features theoretically. A large number of simulated GLONASS signal experiments show that the acquisition probability increases with the increase in the measurement vector column dimension. Finally, the practical availability of the new method is verified by acquisition experiments with the real record GLONASS signal. The new method can reduce the storage space and energy loss of data transmission. We hope that the new method can be applied to field receivers that need to record and transmit navigation data for a long time.

Performance Evaluation of PPP-AR Method for Engineering Surveys with Embedded GNSS Chipset in a Smartphone

2020 ◽  
Author(s):  
Caneren Gul ◽  
Taylan Ocalan ◽  
Nursu Tunalioglu
Keyword(s):  
Satellite System ◽  
Time Interval ◽  
Dual Frequency ◽  
Economic Market ◽  
The World ◽  
Positioning Method ◽  
Gnss Receivers ◽  
Point Positioning ◽  
Global Navigation Satellite ◽  
Gnss Observations

<p>Today, traditional Precise Point Positioning (PPP) method with high-cost geodetic grade Global Navigation Satellite System (GNSS) receivers has been used commonly for surveying, navigation, geodesy, geophysics and other engineering applications where dm-cm level accuracy is required. On the other hand, while smartphones have created a growing economic market in the world, they serve positioning, navigation and timing (PNT) services in varying accuracy levels to the users besides many other facilities. One of the most significant components of the smartphones involving multi-sensors for outdoor point-positioning and navigation is the embedded GNSS chipset. Especially, the world’s first dual-frequency GNSS smartphone produced by Xiaomi in May 2018, so-called Xiaomi Mi 8, brings a new aspect to PNT applications. In this study, a smartphone with dual-frequency embedded GNSS chipset was used to analyze the performance of PPP-Ambiguity Resolution (PPP-AR) method in engineering surveys. With respect to study aim, simultaneous static GNSS observations gathered with a geodetic grade GNSS receiver and a smartphone were conducted within a test setup. The static GNSS observations were repeated for 3 days and the campaign duration was 2 hours per day at the same daily time interval. All the raw GNSS observations were converted into Receiver Independent Exchange Format (RINEX) and processed by the relative point positioning method as a reference solution initially. Later, all observations were processed by the PPP-AR method. A widely used online post-processing GNSS service, namely CSRS-PPP, which was updated in August 2018 (GPSPACE to SPARK) were employed for PPP-AR solutions. As a conclusion, we analyze the performance of the embedded dual frequency GNSS chipset and assess the feasibility of them in different engineering surveys.</p><p><strong>Keywords:</strong> Smartphone Positioning, PPP-AR, Embedded GNSS Chipset, Dual-frequency, Engineering Surveys</p>

First Preliminary Fast Static Ambiguity Resolution Results of Medium-Baseline with Triple-Frequency Beidou Wavebands

2014 ◽  
Vol 67 (6) ◽  
pp. 1109-1119 ◽  
Author(s):  
Shengyue Ji ◽  
Xiaolong Wang ◽  
Ying Xu ◽  
Zhenjie Wang ◽  
Wu Chen ◽  
...  
Keyword(s):  
Frequency Band ◽  
Ambiguity Resolution ◽  
Past Research ◽  
Satellite System ◽  
Tropospheric Delay ◽  
Dual Frequency ◽  
Long Distance ◽  
Triple Frequency ◽  
Global Navigation Satellite ◽  
Better Than

Fast high precision relative Global Navigation Satellite System (GNSS) positioning is very important to various applications and ambiguity resolution is a key requirement. It has been a continuing challenge to determine and fix GNSS carrier-phase ambiguity, especially for medium- and long-distance baselines. In past research, with dual-frequency band Global Positioning System (GPS), it is almost impossible for fast ambiguity resolution of medium- and long-distance baselines mainly due to the ionospheric and tropospheric effects. With the launch of the BeiDou system, triple-frequency band GNSS observations are available for the first time. This research aims to test the ambiguity resolution performance with BeiDou triple-frequency band observations. In this research, two mathematical models are compared: zenith tropospheric delay as an unknown parameter versus corrected tropospheric delay. The ambiguity resolution performance is investigated in detail with BeiDou observations. Different distance baselines are tested: 45 km, 70 km and 100 km and the performances are investigated with different elevation cut-off angles. Also the performance with BeiDou alone and combined BeiDou and GPS are compared. Experimental results clearly show that with practical observations of triple-frequency bands, ambiguity of medium- or long-distance baselines can be fixed. The results also show that: the performance of ambiguity resolution with an elevation cutoff angle of 20° is much better than that of 15°; The performance with tropospheric effect corrected is slightly better than that with tropospheric effect as an estimated parameter; Dual-frequency band GPS observations will benefit ambiguity resolution of integrated BeiDou and GPS.

scholarly journals First simulations of day-to-day variability of mid-latitude sporadic E layer structures

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Satoshi Andoh ◽  
Akinori Saito ◽  
Hiroyuki Shinagawa ◽  
Mitsumu K. Ejiri
Keyword(s):  
Three Dimensional ◽  
Lower Ionosphere ◽  
Atmospheric Tides ◽  
Ionospheric Model ◽  
Radio Waves ◽  
Metallic Ions ◽  
Long Distance ◽  
Distance Communication ◽  
Sporadic E ◽  
Realistic Information

Abstract We present the first simulations that successfully reproduce the day-to-day variability of the mid-latitude sporadic E ($$E_s$$ E s ) layers. $$E_s$$ E s layers appearing in the lower ionosphere have been extensively investigated to monitor and forecast their effects on long-distance communication by radio waves. Although it is widely accepted that the atmospheric tides are important in generating the $$E_s$$ E s layers, no simulations to date have reproduced the $$E_s$$ E s layers observed on a certain day. This is due to the lack of the combination of realistic information on the atmospheric tides in the lower ionosphere and a three-dimensional numerical ionospheric model that can simulate the precise transport of metallic ions. We developed a numerical ionospheric model coupled with the neutral winds from the GAIA (Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy). The fundamental structures and the day-to-day variations of the $$E_s$$ E s layers observed by a $$\hbox {Ca}^+$$ Ca + lidar are well-reproduced in the simulations.

scholarly journals Isla del Coco, on Cocos Plate, converges with Isla de San Andrés, on the Caribbean Plate, at 78mm/yr

2017 ◽  
pp. 33-41
Author(s):  
Mariano Protti ◽  
Víctor González ◽  
Jeffrey Freymueller ◽  
Sarah Doelger
Keyword(s):  
Steady Motion ◽  
Satellite System ◽  
Plate Motion ◽  
Time Interval ◽  
Caribbean Plate ◽  
Cocos Plate ◽  
Position Time Series ◽  
The Caribbean ◽  
Global Navigation Satellite ◽  
San Andres

Isla del Coco is the only land mass of the Cocos Plate that emerges above sea level. This makes it the only place where Cocos Plate motion can be measured using Global Navigation Satellite System (GNSS) monitoring. Global Positioning System (GPS) observations have been carried out sporadically over more than two decades on Isla del Coco, allowing precise measurement of the motion of the Cocos Plate. Recently, in May 2011, a continuous GPS station was built and instrumented at Isla del Coco, in Wafer Bay, by OVSICORI-UNA and UNAVCO, as part of the COCONet regional GNSS network. Position time series from this CGPS station (ISCO: Isla del Coco) show a steady motion of Isla del Coco at a speed of 90.9±1.5mm/yr in the N35oE direction in ITRF2008 and convergence with the Caribbean Plate at 78±1mm/yr. This result is consistent with the findings of the earliest GPS studies, and agrees within uncertainty with the estimated convergence rate of 76.4±x mm/ yr of the MORVEL plate motion model. MORVEL is based on an average over the last 780,000 years, and our result suggests that Cocos-Caribbean plate motions have been constant over that time interval. Citation: Protti, M., V. González, J. Freymueller & S. Doelger. 2012. Isla del Coco, on Cocos Plate, converges with San Andres Island, on the Caribbean Plate, at 78mm/yr. Rev. Biol. Trop. 60 (Suppl. 3): 33-41. Epub 2012 Dec 01.

scholarly journals Ionospheric S4 Scintillations from GNSS Radio Occultation (RO) at Slant Path

2020 ◽  
Vol 12 (15) ◽  
pp. 2373
Author(s):  
Dong L. Wu
Keyword(s):  
Radio Occultation ◽  
Satellite System ◽  
Ionospheric Scintillation ◽  
Equatorial Plasma Bubbles ◽  
Low Latitudes ◽  
Slant Path ◽  
Sporadic E ◽  
Dip Angle ◽  
Navigation Signals ◽  
Global Navigation Satellite

Ionospheric scintillation can significantly degrade the performance and the usability of space-based communication and navigation signals. Characterization and prediction of ionospheric scintillation can be made from the Global Navigation Satellite System (GNSS) radio occultation (RO) technique using the measurement from a deep slant path where the RO tangent height (ht) is far below the ionospheric sources. In this study, the L–band S4 from the RO measurements at ht = 30 km is used to infer the amplitude scintillation on the ground. The analysis of global RO data at ht = 30 km shows that sporadic–E (Es), equatorial plasma bubbles (EPBs), and equatorial spread–F (ESF) produce most of the significant S4 enhancements, although the polar S4 is generally weak. The enhanced S4 is a strong function of local time and magnetic dip angle. The Es–induced daytime S4 tends to have a negative correlation with the solar cycle at low latitudes but a positive correlation at high latitudes. The nighttime S4 is dominated by a strong semiannual variation at low latitudes.

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