scholarly journals Derivation of TEC and estimation of instrumental biases from GEONET in Japan

2003 ◽  
Vol 21 (10) ◽  
pp. 2083-2093 ◽  
Author(s):  
G. Ma ◽  
T. Maruyama
Keyword(s):  
Electron Content ◽  
Dual Frequency ◽  
Simple Method ◽  
Total Electron ◽  
Radio Science ◽  
Ionospheric Total Electron Content ◽  
Gps Satellites ◽  
Observation Network ◽  
Instruments And Techniques ◽  
High Degree

Abstract. This paper presents a method to derive the ionospheric total electron content (TEC) and to estimate the biases of GPS satellites and dual frequency receivers using the GPS Earth Observation Network (GEONET) in Japan. Based on the consideration that the TEC is uniform in a small area, the method divides the ionosphere over Japan into 32 meshes. The size of each mesh is 2° by 2° in latitude and longitude, respectively. By assuming that the TEC is identical at any point within a given mesh and the biases do not vary within a day, the method arranges unknown TECs and biases with dual GPS data from about 209 receivers in a day unit into a set of equations. Then the TECs and the biases of satellites and receivers were determined by using the least-squares fitting technique. The performance of the method is examined by applying it to geomagnetically quiet days in various seasons, and then comparing the GPS-derived TEC with ionospheric critical frequencies (foF2). It is found that the biases of GPS satellites and most receivers are very stable. The diurnal and seasonal variation in TEC and foF2 shows a high degree of conformity. The method using a highly dense receiver network like GEONET is not always applicable in other areas. Thus, the paper also proposes a simpler and faster method to estimate a single receiver’s bias by using the satellite biases determined from GEONET. The accuracy of the simple method is examined by comparing the receiver biases determined by the two methods. Larger deviation from GEONET derived bias tends to be found in the receivers at lower (<30° N) latitudes due to the effects of equatorial anomaly.Key words. Ionosphere (mid-latitude ionosphere; instruments and techniques) – Radio science (radio-wave propagation)

Geometric determination of ionospheric total electron content from dual frequency radar sounding measurements

2019 ◽  
Vol 178 ◽  
pp. 104696 ◽  
Author(s):  
Kirk M. Scanlan ◽  
Cyril Grima ◽  
Gregor Steinbrügge ◽  
Scott D. Kempf ◽  
Duncan A. Young ◽  
...  
Keyword(s):  
Total Electron Content ◽  
Electron Content ◽  
Dual Frequency ◽  
Total Electron ◽  
Ionospheric Total Electron Content

scholarly journals Variations of the ionospheric TEC using simultaneous measurements from the China Crustal Movement Observation Network

2012 ◽  
Vol 30 (10) ◽  
pp. 1423-1433 ◽  
Author(s):  
Y. W. Wu ◽  
R. Y. Liu ◽  
B. C. Zhang ◽  
Z. S. Wu ◽  
J. S. Ping ◽  
...  
Keyword(s):  
Crustal Movement ◽  
Topside Ionosphere ◽  
Electron Content ◽  
Equatorial Anomaly ◽  
Total Electron ◽  
Movement Observation ◽  
The North ◽  
Ionospheric Total Electron Content ◽  
Observation Network ◽  
Two Peaks

Abstract. Variations of the ionospheric Total Electron Content (TEC) over China are investigated using the TEC data obtained from China Crustal Movement Observation Network in the year 2004. The results show a single-peak occurred in post-noon for the diurnal variation and two peaks exit around two equinox points, respectively, for the seasonal variation. Overall, the values of TEC increased from the north to the south of China. There were small but clear longitudinal differences in both sides of the longitudes with zero magnetic declination. The intensity of the day-to-day variation of TEC was not a monotonic change along the latitudes. It was usually weaker in the middle of China than that in the north or south. Comparing with the maximum F-layer electron density (NmF2) derived from the ionosonde stations in China, it is found that the day-to-day variation of TEC was less significant than that of NmF2, and that the northern crest of the equatorial anomaly identified from the NmF2 data can reach Guangzhou-region. While, the TEC crest was hardly observed in the same location. This is probably caused by the tilt of topside ionosphere near the northern anomaly crest region at lower latitudes.

A Study Of Ionospheric GPS Scintillation During Solar Maximum at UTeM Station

2015 ◽  
Vol 73 (1) ◽  
Author(s):  
Emad F. Aon ◽  
A. R. Othman ◽  
Y. H. Ho ◽  
R. Q. Shaddad
Keyword(s):  
Solar Maximum ◽  
Satellite System ◽  
Equatorial Region ◽  
Ionospheric Scintillation ◽  
Electron Content ◽  
Dual Frequency ◽  
Ionospheric Layer ◽  
Total Electron ◽  
Gps Satellites ◽  
Gps Scintillation

Wireless signals propagated along global positioning system (GPS) channel are affected by ionospheric electron density irregularities such that GPS signals may experience amplitude and phase fluctuations. The global navigation satellite system (GNSS), ionospheric scintillation, and total electron content (TEC) monitor (GISTM) receiver has been installed at UTeM, Malaysia (2.3139°N, 102.3183°E) for monitoring ionospheric scintillation at several frequencies. In this paper, the GPS ionospheric scintillations are concerned for the dual frequency L1 (fL1 = 1.57542 GHz) and L2C (fL2= 1.2276 GHz).  Ionospheric scintillation data has been collected during solar maximum cycle 2013-2014 for six months October 2013–March 2014. Solar activities significantly impact the ionospheric GPS scintillation, especially in the equatorial region where Malaysia is located. The GPS link is analyzed to investigate how the scintillation increases during the solar maximum cycle. When the sun flux is maximum, the total of electrons is increased in the ionospheric layer and the scintillation values gradually become high. The ionospheric amplitude/phase scintillation, carrier-to-noise (C/No) ratio, and availability of GPS satellites are reported in the proposed experimental GPS model. Consequently, for Malaysia, typical threshold received C/No ratio is 43 dB-Hz, implying that C/No ratio should be greater than 43 dB-Hz to receive good signals at the GPS receiver.

scholarly journals Variations of the ionospheric electron density during the Bhuj seismic event

2004 ◽  
Vol 22 (12) ◽  
pp. 4123-4131 ◽  
Author(s):  
A. Trigunait ◽  
M. Parrot ◽  
S. Pulinets ◽  
F. Li
Keyword(s):  
Electron Density ◽  
Electric Circuit ◽  
Volcanic Eruptions ◽  
Electron Content ◽  
Total Electron ◽  
Radio Science ◽  
Ionospheric Physics ◽  
Gps Satellites ◽  
Before And After ◽  
History Of Geophysics

Abstract. Ionospheric perturbations by natural geophysical activity, such as volcanic eruptions and earthquakes, have been studied since the great Alaskan earthquake in 1964. Measurements made from the ground show a variation of the critical frequency of the ionosphere layers before and after the shock. In this paper, we present an experimental investigation of the electron density variations around the time of the Bhuj earthquake in Gujarat, India. Several experiments have been used to survey the ionosphere. Measurements of fluctuations in the integrated electron density or TEC (Total Electron Content) between three satellites (TOPEX-POSEIDON, SPOT2, SPOT4) and the ground have been done using the DORIS beacons. TEC has been also evaluated from a ground-based station using GPS satellites, and finally, ionospheric data from a classical ionospheric sounder located close to the earthquake epicenter are utilized. Anomalous electron density variations are detected both in day and night times before the quake. The generation mechanism of these perturbations is explained by a modification of the electric field in the global electric circuit induced during the earthquake preparation. Key words. Ionosphere (ionospheric disturbances) – Radio Science (ionospheric physics) – History of geophysics (seismology)

scholarly journals Characteristics of the ionospheric total electron content of the equatorial ionization anomaly in the Asian-Australian region during 1996–2004

2009 ◽  
Vol 27 (10) ◽  
pp. 3861-3873 ◽  
Author(s):  
◽  
◽  
◽  
Keyword(s):  
Total Electron Content ◽  
Local Time ◽  
Dominant Factor ◽  
Electron Content ◽  
Dual Frequency ◽  
Total Electron ◽  
Australian Region ◽  
Ionospheric Total Electron Content ◽  
Equatorial Ionization Anomaly ◽  
Vertical Drift

Abstract. Ionospheric total electron content (TEC) of the equatorial ionization anomaly (EIA) is studied by analyzing dual-frequency signals of the Global Position System (GPS) acquired from a network of receivers around the Asian-Australian region during 1996–2004. The latitude, occurrence time, strength of the most developed EIA crest, and crest-to-trough ratio (CTR) for both the noon and post-sunset sector obtained from a daily TEC contour map have been used to study the solar cycle variations of EIA in the Asian-Australian region. The results reveal that semiannual and seasonal variations were the dominant factor that controls the morphology of the EIA structure which can be identified in the past studies (e.g. Wu et al., 2008). It is also found that the latitude and local time position of the anomaly crest show a hemispheric asymmetry because (a) The northern crest of EIA is expanded during the equinox indicating a weak semiannual variation while the southern crest is inhibited during June–August presenting a strong seasonal variation, and (b) The local time of the northern crest appears ~1.3 h earlier than that of the southern crest in June while showing no difference at December. Solar activity dependence is more evident in the EIA crest region than in the EIA trough region and least in the post-sunset sector at equinox. A seasonal linear relationship is derived between the post-sunset CTR and solar flux, which should be caused by the solar-dependant equatorial E×B vertical drift.

scholarly journals Functional model modification of precise point positioning considering the time-varying code biases of a receiver

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Baocheng Zhang ◽  
Chuanbao Zhao ◽  
Robert Odolinski ◽  
Teng Liu
Keyword(s):  
Precise Point Positioning ◽  
Functional Model ◽  
Geodetic Network ◽  
Temporal Variations ◽  
Gps Data ◽  
Electron Content ◽  
Time Varying ◽  
Dual Frequency ◽  
Total Electron ◽  
Point Positioning

AbstractPrecise Point Positioning (PPP), initially developed for the analysis of the Global Positing System (GPS) data from a large geodetic network, gradually becomes an effective tool for positioning, timing, remote sensing of atmospheric water vapor, and monitoring of Earth’s ionospheric Total Electron Content (TEC). The previous studies implicitly assumed that the receiver code biases stay constant over time in formulating the functional model of PPP. In this contribution, it is shown this assumption is not always valid and can lead to the degradation of PPP performance, especially for Slant TEC (STEC) retrieval and timing. For this reason, the PPP functional model is modified by taking into account the time-varying receiver code biases of the two frequencies. It is different from the Modified Carrier-to-Code Leveling (MCCL) method which can only obtain the variations of Receiver Differential Code Biases (RDCBs), i.e., the difference between the two frequencies’ code biases. In the Modified PPP (MPPP) model, the temporal variations of the receiver code biases become estimable and their adverse impacts on PPP parameters, such as ambiguity parameters, receiver clock offsets, and ionospheric delays, are mitigated. This is confirmed by undertaking numerical tests based on the real dual-frequency GPS data from a set of global continuously operating reference stations. The results imply that the variations of receiver code biases exhibit a correlation with the ambient temperature. With the modified functional model, an improvement by 42% to 96% is achieved in the Differences of STEC (DSTEC) compared to the original PPP model with regard to the reference values of those derived from the Geometry-Free (GF) carrier phase observations. The medium and long term (1 × 104 to 1.5 × 104 s) frequency stability of receiver clocks are also significantly improved.

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