共查询到20条相似文献,搜索用时 15 毫秒
1.
As GPS is modernizing, there are currently fourteen satellites transmitting L2C civil code and seven satellites transmitting L5 signal. While the GPS observables are subject to several sources of errors, the ionosphere is one of the largest error sources affecting GPS signals. Small irregularities in the electrons density along the GPS radio signal propagation path cause ionospheric scintillation that is characterized by rapid fluctuations in the signal amplitude and phase. The ionospheric scintillation effects are stronger in equatorial and high-latitude geomagnetic latitude regions and occur mainly due to equatorial anomaly and solar storms. Several researchers have analyzed the L2C signal quality since becoming available in December, 2005. We analyze the performance of L2C using GPS data from stations in the equatorial region of Brazil, which is subject of weak, moderate and strong ionospheric scintillation conditions. The GPS data were collected by Septentrio PolaRxS–PRO receivers as part of the CIGALA/CALIBRA network. The analysis was performed as a function of scintillations indexes S4 and Phi60, lock time (time interval in seconds that the carrier phase is tracked continuously without cycle slips), multipath RMS and position variation of precise point positioning solutions. The analysis shows that L2C code solutions are less affected by multipath effects than that of P2 when data are collected under weak ionospheric scintillation effects. In terms of analysis of positions, the kinematic PPP results using L2C instead P2 codes show accuracy improvements up to 33 % in periods of weak or strong ionospheric scintillation. When combining phase and code collected under weak scintillation effects, the results by applying L2C against P2 provide improvement in accuracy up to 59 %. However, for data under strong scintillation effects, the use of L2C for PPP with code and phase does not provide improvements in the positioning accuracy. 相似文献
2.
3.
Local variability in total electron content can seriously affect the accuracy of GNSS real-time applications. We have developed
software to compute the positioning error due to the ionosphere for all baselines of the Belgian GPS network, called the Active
Geodetic Network (AGN). In a first step, a reference day has been chosen to validate the methodology by comparing results
with the nominal accuracy of relative positioning at centimeter level. Then, the effects of two types of ionospheric disturbances
on the positioning error have been analyzed: (1) Traveling ionospheric disturbances (TIDs) and (2) noise-like variability
due to geomagnetic storms. The influence of baseline length on positioning error has been analyzed for these three cases.
The analysis shows that geomagnetic storms induce the largest positioning error (more than 2 m for a 20 km baseline) and that
the positioning error depends on the baseline orientation. Baselines oriented parallel to the propagation direction of the
ionospheric disturbances are more affected than others. The positioning error due to ionospheric small-scale structures can
be so identified by our method, which is not always the case with the modern ionosphere mitigation techniques. In the future,
this ionospheric impact formulation could be considered in the development of an integrity monitoring service for GNSS relative
positioning users. 相似文献
4.
Medium-scale traveling ionospheric disturbances observed by GPS receiver network in Japan: a short review 总被引:2,自引:0,他引:2
Medium-scale traveling ionospheric disturbances (MSTID) are wave-like perturbations of the ionospheric plasma with wavelengths
of several hundred kilometres and velocities of several hundred metres per second. MSTID is one of the most common ionospheric
phenomena that generally induce the perturbations of ionospheric total electron content (TEC) by ∼1016 electron/m2, which corresponds to ∼54 ns (16.2 cm) delay at GPS L1 signal. In the past decade, several new characteristics on MSTIDs
have been revealed by the TEC observations using the dense GPS receiver network in Japan. In this paper, we provide a short
review of these new observations and summarize the morphological characteristics of MSTIDs in Japan. 相似文献
5.
6.
Dudy D. Wijaya Haris Haralambous Christina Oikonomou Wedyanto Kuntjoro 《Journal of Geodesy》2017,91(9):1117-1133
The critical frequency of ionospheric F2 layer (foF2) is a measure of the highest frequency of radio signal that may be reflected back by the F2 layer, and it is associated with ionospheric peak electron density in the F2 layer. Accurate long-term foF2 variations are usually derived from ionosonde observations. In this paper, we propose a new method to observe foF2 using a stand-alone global positioning system (GPS) receiver. The proposed method relies on the mathematical equation that relates foF2 to GPS observations. The equation is then implemented in the Kalman filter algorithm to estimate foF2 at every epoch of the observation (30-s rate). Unlike existing methods, the proposed method does not require any additional information from ionosonde observations and does not require any network of GPS receivers. It only requires as inputs the ionospheric scale height and the modeled plasmaspheric electron content, which practically can be derived from any existing ionospheric/plasmaspheric model. We applied the proposed method to estimate long-term variations of foF2 at three GPS stations located at the northern hemisphere (NICO, Cyprus), the southern hemisphere (STR1, Australia) and the south pole (SYOG, Antarctic). To assess the performance of the proposed method, we then compared the results against those derived by ionosonde observations and the International Reference Ionosphere (IRI) 2012 model. We found that, during the period of high solar activity (2011–2012), the values of absolute mean bias between foF2 derived by the proposed method and ionosonde observations are in the range of 0.2–0.5 MHz, while those during the period of low solar activity (2009–2010) are in the range of 0.05–0.15 MHz. Furthermore, the root-mean-square-error (RMSE) values during high and low solar activities are in the range of 0.8–0.9 MHz and of 0.6–0.7 MHz, respectively. We also noticed that the values of absolute mean bias and RMSE between foF2 derived by the proposed method and the IRI-2012 model are slightly larger than those between the proposed method and ionosonde observations. These results demonstrate that the proposed method can estimate foF2 with a comparable accuracy. Since the proposed method can estimate foF2 at every epoch of the observation, it therefore has promising applications for investigating various scales (from small to large) of foF2 irregularities. 相似文献
7.
A. G. Pavelyev J. Wickert Y. A. Liou Ch. Reigber T. Schmidt K. Igarashi A. A. Pavelyev S. S. Matyugov 《GPS Solutions》2005,9(2):96-104
A local mechanism for strong ionospheric effects on radio occultation (RO) global positioning satellite system (GPS) signals is described. Peculiar zones centered at the critical points (the tangent points) in the ionosphere, where the gradient of the electron density is perpendicular to the RO ray trajectory, strongly influence the amplitude and phase of RO signals. It follows from the analytical model of local ionospheric effects that the positions of the critical points depend on the RO geometry and the structure of the ionospheric disturbances. Centers of strong ionospheric influence on RO signals can exist, for example, in the sporadic E-layers, which are inclined by 3–6° relative to the local horizontal direction. Also, intense F2 layer irregularities can contribute to the RO signal variations. A classification of the ionospheric influence on the GPS RO signals is introduced using the amplitude data, which indicates different mechanisms (local, diffraction, etc.) for radio waves propagation. The existence of regular mechanisms (e.g., local mechanism) indicates a potential for separating the regular and random parts in the ionospheric influence on the RO signals. 相似文献
8.
9.
GPS观测数据中的仪器偏差对确定电离层延迟的影响及处理方法 总被引:48,自引:5,他引:43
本文通过设计不同的计算方案详细分析了GPS观测中的仪器偏差对确定电离层延迟的影响,利用多天实测数据,结合仪器偏差与电离层延迟的分离方法,探讨了仪器偏差的稳定性,并提出了一种静态确定电离层延迟的方案。算例表明它能有效克服仪器偏差影响。 相似文献
10.
On the effects of the ionospheric disturbances on precise point positioning at equatorial latitudes 总被引:3,自引:2,他引:1
B. Moreno S. Radicella M. C. de Lacy M. Herraiz G. Rodriguez-Caderot 《GPS Solutions》2011,15(4):381-390
In precise point positioning (PPP), the ionospheric delay is corrected in a first-order approximation from GPS dual-frequency
observations, which should eliminate almost completely the ionosphere as a source of error. However, sudden plasma density
variations can adversely affect the GPS signal, degrading accuracy and reliability of positioning techniques. The occurrence
of plasma density irregularities is frequent at equatorial latitudes and is reflected in large total electron content (TEC)
variations. We study the relation between large changes in the rate of TEC (ROT) and positioning errors in single-epoch PPP.
At equatorial latitudes and during post-sunset hours, the estimated altitudes contain errors of several meters for a single-epoch
position determination, and latitude and longitude estimates are also degraded. These results have been corroborated by the
online CSRS-PPP (NRCan) program. Moreover, abrupt changes in the satellite geometry have been discarded as possible cause
of such errors, suggesting an apparent relation between the occurrence of large ROT and degraded position estimates. 相似文献
11.
Statistics of GPS ionospheric scintillation and irregularities over polar regions at solar minimum 总被引:2,自引:1,他引:1
A statistical study of the occurrence characteristic of GPS ionospheric scintillation and irregularity in the polar latitude
is presented. These measurements were made at Ny-Alesund, Svalbard [78.9°N, 11.9°E; 75.8°N corrected geomagnetic latitude
(CGMLat)] and Larsemann Hills, East Antarctica (69.4°S, 76.4°E; 74.6°S CGMLat) during 2007–2008. It is found that the GPS
phase scintillation and irregularity activity mainly takes place in the months 10, 11 and 12 at Ny-Alesund, and in the months
5, 6 at Larsemann Hills. The seasonal pattern of phase scintillation with respect to the station indicates that the GPS phase
scintillation occurrence is a local winter phenomenon, which shows consistent results with past studies of 250 MHz satellite
beacon measurements. The occurrence rates of GPS amplitude scintillation at the two stations are below 1%. A comparison with
the interplanetary magnetic field (IMF) B
y and B
z components shows that the phase scintillation occurrence level is higher during the period from later afternoon to sunset
(16–19 h) at Ny-Alesund, and from sunset to pre-midnight (18–23 h) at Larsemann Hills for negative IMF components. The findings
seem to indicate that the dependence of scintillation and irregularity occurrence on geomagnetic activity appears to be associated
with the magnetic local time (MLT). 相似文献
12.
13.
为了建立更高精度的电离层T EC预报模型,利用IGS数据中心提供的平静期与磁暴期电离层T EC原始序列,提出基于奇异谱分析法(SSA)与Elman神经网络结合的电离层T EC预报模型.实验结果表明,在电离层平静期T EC的预报精度上,SSA-Elman组合模型的精度更加稳定,预测残差值在2 T ECu以内;在电离层磁暴... 相似文献
14.
Impact of the Halloween 2003 ionospheric storm on kinematic GPS positioning in Europe 总被引:2,自引:0,他引:2
N. Bergeot C. Bruyninx P. Defraigne S. Pireaux J. Legrand E. Pottiaux Q. Baire 《GPS Solutions》2011,15(2):171-180
Using dual-frequency data from 36 GPS stations from the EUREF Permanent Network (EPN), the influence of the October 30, 2003
Halloween geomagnetic storm on kinematic GPS positioning is investigated. The Halloween storm induced ionospheric disturbances
above the northern part of Europe and Scandinavia. It is shown that kinematic position repeatabilities for this period are
mainly affected for stations in northern Europe with outliers reaching 12 cm in the horizontal, and 26 cm in the vertical.
These magnitudes are shown to be possibly due to the second-order ionospheric delays on GPS signals, not accounted for in
the kinematic GPS positioning analysis performed. In parallel, we generate hourly TEC (Total Electron Content) maps on a 1° × 1°
grid using the dense EPN network. These TEC maps do not use any interpolation but provide a high resolution in the time and
space and therefore allow to better evidence small structures in the ionosphere than the classical 2-hourly 2.5° × 5° grid
Global Ionospheric TEC Maps (GIM). Using the hourly 1° × 1° TEC maps, we reconstruct and refine exactly the zones of intense
ionosphere activity during the storm, and we show the correlation between the ionospheric activity and assess the quality
of GPS-based kinematic positioning performed in the European region. 相似文献
15.
16.
In this paper, ionospheric disturbance data from a local GPS network in Hong Kong (low latitude region) are studied in the
solar maximum period (2001–2003). The spatial and temporal distributions of the disturbances in Hong Kong are investigated.
It is found that strong ionospheric disturbances occur frequently during the solar maximum period, particularly around March
and September, and concentrate at the region around geographic latitude 22°N (geomagnetic latitude 12°N). The effects of the
disturbances on GPS geodetic receivers, such as loss of lock and measurement noise level, are also analyzed for the 3-year
period. It shows that the measurement noise level and the number of losses of lock in GPS data increase dramatically during
ionospheric disturbance periods. The behaviors of different types of GPS receivers during the disturbances are also compared. 相似文献
17.
The network-based GPS technique provides a broad spectrum of corrections to support RTK (real-time kinematic) surveying and
geodetic applications. The most important among them are the ionospheric corrections generated in the reference network. The
accuracy of these corrections depends upon the ionospheric conditions and may not always be sufficient to support ambiguity
resolution (AR), and hence accurate GPS positioning. This paper presents the analyses of the network-derived ionospheric correction
accuracy under extremely varying – quiet and stormy – geomagnetic and ionospheric conditions. In addition, the influence of
the correction accuracy on the instantaneous (single-epoch) and on-the-fly (OTF) AR in long-range RTK GPS positioning is investigated,
and the results, based on post-processed GPS data, are provided. The network used here to generate the ionospheric corrections
consists of three permanent stations selected from the Ohio Continuously Operating Reference Stations (CORS) network. The
average separation between the reference stations was ∼200 km and the test baseline was 121 km long. The results show that,
during the severe ionospheric storm, the correction accuracy deteriorates to the point when the instantaneous AR is no longer
possible, and the OTF AR requires much more time to fix the integers. The analyses presented here also outline the importance
of the correct selection of the stochastic constraints in the rover solution applied to the network-derived ionospheric corrections. 相似文献
18.
Understanding the role of the ionospheric delay in single-point single-epoch GPS coordinates 总被引:1,自引:0,他引:1
Elsa Mohino 《Journal of Geodesy》2008,82(1):31-45
The ionospheric delay is the main source of error for single-point single-epoch (SPSE) GPS positioning when using single-frequency
receivers. In contrast to the common slant approach, in this article we focus on its effect in final coordinates through the
study of bias propagation in SPSE positioning: we first show an analytical resolution for the propagation problem with highly
symmetric satellite configurations. To overcome some of the disadvantages of this first method, we use Santerre’s technique
and, finally, present a new numerical methodology that allows us to generalize for a real geometry and obtain an average ionospheric
positioning error over a given site. From the results obtained, four working hypotheses that relate the ionospheric shape
above the receiver with final position errors are presented and tested. These four hypotheses, which agree with average ionospheric
positioning error in 95% of the studied cases, can be related to the construction of the design matrix. Finally, these hypotheses
have been used to address a situation where the ionospheric delay is corrected with an ionospheric model. 相似文献
19.
本文对FJCORS基准站定位误差序列进行了分析,发现观测误差呈明显的季节性变化,峰值出现在7月,同时分析了定位误差与电离层VTEC和气象要素的关系。结果表明,定位误差与VTEC不相关,而与气象要素存在较强的相关性,气压降低或气温、水汽压升高直接导致误差呈线性增加。 相似文献