Session 6 - Space Weather effects on GNSS and precise positioning
Claudia Borries, J. Berdermann (German Aerospace Center)
Tuesday 15/11, 10:00-13:00
One of the most dominant error sources for GNSS applications is the Ionosphere. It does not only affect standard GNSS applications and differential GNSS but also high-accuracy demanding applications like the Precise Point Positioning (PPP) and Real Time Kinematics (RTK). Next to the common signal delay, the Ionosphere can cause e.g. loss of lock in case of scintillation events or produce hazardous misleading information in augmentation systems due to strong ionospheric gradients. Higher order ionospheric effects limit the PPP. Today, a large variety of products and models is already in place to reduce the ionospheric error on GNSS applications. However, often there is still a gap between the currently available products and their actual usage in GNSS applications. This session aims to communicate the status of the currently available techniques for ionospheric error correction. Reports on the impact of the ionosphere to GNSS application and the formulation of derived requirements on ionospheric services are very welcome. Furthermore we also encourage the presentations of available products for mitigating the ionospheric impact on GNSS as well as related research on forecast and modelling of the Ionosphere.
Tuesday November 15, 10:00 - 11:00, Poster AreaTalks
Tuesday November 15, 11:00 - 13:00, MercatorClick here to toggle abstract display in the schedule
Talks : Time scheduleTuesday November 15, 11:00 - 13:00, Mercator
|11:00||Mitigation of ionospheric scintillation effects on GNSS positioning at low latitudes||Vadakke veettil, S et al.||Invited Oral|
| ||Sreeja Vadakke Veettil and Marcio Aquino|
| ||Nottingham Geospatial Institute, University of Nottingham, Nottingham, UK|
| ||Global Navigation Satellite Systems (GNSS, such as GPS, GLONASS, GALILEO, Beidou) underpin a number of modern life activities, providing positioning accuracy that can support from mass of market to mission-critical high accuracy applications. PPP (Precise Point Positioning) is a carrier-based GNSS technique that enables high accuracy positioning by incorporating external information in the user solution. The external information typically includes highly accurate (satellites clock and orbit) products derived from global networks and available for free (e.g. http://igs.org/rts) or commercially (e.g. http://www.starfix.com). Currently, the atmospheric correction is not normally part of the information available from the aforementioned global networks to assist the PPP solution, but rather has to be estimated through a start-up process that can take tens of minutes, leading to a barrier for PPP’s wide adoption by industry. This is because in PPP the atmospheric error, the ionospheric component in particular, can only be distinguished from other errors when a change in satellite geometry allows separation of the constant carrier phase ambiguity from the other errors. The ionosphere, ionized part of the upper atmosphere, is critical in PPP, due to its high variability and to disturbances such as scintillation (characterised by fluctuations in signal amplitude and phase) that can affect the satellite signals propagation and thereby degrade the positioning accuracy. This paper describes a technique to mitigate the effects of ionospheric scintillation on PPP, whereby the variance of the output error of the GNSS receiver DLL (Delay Locked Loop) and PLL (Phase Locked Loop), respectively, are used to modify the least squares stochastic model used by the receiver to compute position. The paper presents results of a study carried out at a low latitude station in Brazil, where this technique was applied and evaluated. |
|11:15||Regional forecast of ionospheric scintillation dedicated to offshore operators||Yaya, P et al.||Oral|
| ||Philippe Yaya, Louis Hecker|
| ||CLS (Collecte Localisation Satellites), Ramonville Saint-Agne, France|
| ||One of CLS Space Weather services deals with the estimation of ionospheric scintillation at a regional scale. In the field of offshore activity, the precision and reliability on GNSS positioning is of higher interest. In order to address this need, a dedicated empirical model has been developed for the Guinean Gulf, in Western Africa. Based on measurements from public and private geodetic receivers, it allows to deliver an estimation of the level of amplitude scintillation 6 hours in advance, with a tailored alert to the GNSS users. The present work discusses the performance of the model, its limitation and future improvements. A model for the Brazilian eastern coast is under development and its first results are also presented.|
|11:30||High-Latitude Scintillations and Electron Density Gradients Impact on GNSS Receiver Performance||Høeg, P et al.||Invited Oral|
| ||Per Høeg, Tibor Durgonics, Hans-Henrik von Benzon|
| ||Technical University of Denmark (DTU), DTU Space, 2800 Kgs. Lyngby, Denmark|
| ||During ionospheric disturbed conditions at high latitudes scintillations can be severe and impact satellite-based GNSS positioning, leading to receiver loss of lock. Scintillations and their spectral characteristics is a function of amplitude, phase, polarization, and angle of arrival of the GNSS signal, which in total can affect the performance of the receiver phase lock loop (PLL) through the receiver loop bandwidth and the PLL integration time.
The ionospheric scintillations are traditionally quantified by indices related to amplitude scintillations (S4), phase scintillations (σφ), and the rate of change in the observed total electron content (ROTI). Our study focuses on the high latitude ionosphere, where scintillations, especially phase scintillations, and fast varying electron densities are prominent during magnetic storms. We present observations acquired from a network of Greenland GNSS stations (GNET) during storm time periods. Regional 2D amplitude and phase scintillation index maps will be presented during calm and storm times to quantify the large changes in the received signals. We will present a set of indices derived from the power spectra of the signals and compare them with the traditional indices.
The corner frequency of the power spectrum is a function of the Fresnel radius and the drift speed of the irregularities. While the slope of the power spectrum is related to the Fresnel oscillations. We will present how the spectral characteristics of the scintillations act under large total electron content (TEC) gradients, how physical parameters can be extracted from the power spectra, and how the principles governing the parameters of the corner frequencies and power spectra slopes vary during strong ionospheric storms. This will be compared to properties of simulated GNSS signals computed by the Fast Scintillation Mode model (FSM). The model simulates ionospheric scintillation characteristics during fast changing geophysical conditions driven by enhanced scintillations and electron density gradients.
|11:45||Data reduction techniques for Ionosphere anomaly characterization using multi-GNSS||Lalgudi gopalakrishnan, G et al.||Invited Oral|
| ||Ganesh Lalgudi Gopalakrishnan, Joachim Feltens|
| ||Telespazio VEGA Deutschland GmbH, Telespazio VEGA Deutschland GmbH c/o European Space Operations Centre (ESOC)|
| ||The phenomenon of Ionosphere anomalies such as plasma bubbles, blob, patches, gradients and scintillation are important to understand for many applications. It is common to assume empirical relationships between space weather events, Ionosphere anomalies and their impact on GNSS users. The likelihood of a specific geometrical interpretation of anomalies (especially the spatial gradients) is highly desired by the fraternity which uses empirical models to predict the worst case impact of such anomalies on GNSS users. New measurement processing techniques for data reduction are presented in this paper to characterize the magnitude and the dynamics of these anomalies. The main challenge in such characterization is that such anomalies are often short lived and thus would have to be simultaneously observed, measured and assimilated from a geographically diverse network.
This paper provides initial description of the accomplished spatial and temporal filtering techniques in the data assimilation process. In this paper the main intention is to reduce multi-GNSS data into observables which provide insight into the dimensionality of anomalies. Using only GNSS data has the inherent disadvantage that the regions of ionosphere observed is constrained by the receiver-satellite relative geometry. Even though the receiver may be placed to some extent in conducive areas to probe ionosphere, it is often impractical to gather data over oceans (\~70\% of the world is covered by the oceans !). Multi-GNSS provides an improved diversity over single GNSS constellation for the study of Ionosphere using dual frequency measurements. Abundant literature can be found on quantifying the effect of ionosphere anomalies for applications, development of threat models.
In order to characterize the impact of anomalies for safety-of-life applications, reliable statistics are required from a period of anomalous ionosphere. It is also useful to consider other features from GNSS data surrounding the period and location of ionosphere anomalies. In this work, the clustered samples from ionosphere gradients are calculated for a period of medium ionosphere activity in August - September 2013 and compared to those obtained during 2003. Since the nature of ionosphere is such that it can cause both high and low gradients, Ionosphere anomalies cannot be classified just on the basis of their magnitude of gradients. Moreover if the gradients are computed using dual frequency GNSS data, then there are possibilities that a majority of the samples which show signs of high magnitude gradients are simply caused due to measurement, modelling or processing inconsistencies. In this paper, the authors demonstrate this aspect of analysis of the ionosphere gradients computed using multi-frequency GNSS data.|
|12:00||Relation between the strength of ionospheric plasma density gradients and the loss of GPS signals onboard the Swarm satellites||Stolle, C et al.||Invited Oral|
| ||Claudia Stolle, Chao Xiong, Christian Siemes|
| ||GFZ Potsdam, Germany; RHEA for ESA, ESTEC/Netherlands |
| ||In this study we evaluate the performance of the GPS receivers onboard the ESA’s Swarm satellite mission with launch in November 2013, and put special ephasize on events of loss of GPS signals on all chanels. Our result shows that the Swarm satellites encountered most of these losses at low latitudes between ±5°- ±20° magnetic latitude, forming two bands along the magnetic equator; and these low-latitudes events mainly appear around post-sunset hours from 1900-2200 local time. All these events are related to post-sunset equatorial plasma irregularities (EPIs), showing absolute density depletion larger than 10×1011 m-3. Few events of GPS signal loss have been observed at high latitude, mainly around magnetic local noon. These events are possibly related to large spatial density gradient at high latitudes, e.g. due to the polar patches or magnetic disturbances. We further experienced that the loss of signals reduced after different GPS receiver settings had been updated onboard the Swarm satellites; however these more recent periods of the mission also coincide with lower electron density background due to declining solar cycle, both making GPS loss events less likely.
|12:15||Near-real time detection of solar radio burst impacting the GNSS signal reception||Chevalier, J et al.||Oral|
| ||Jean-Marie Chevalier, Nicolas Bergeot, Christophe Marqué and Carine Bruyninx|
| ||Royal Observatory of Belgium|
| ||Intense solar radio bursts (SRBs) emitted at L-band frequencies can affect the carrier-to-noise density C/N0 of Global Navigation Satellite Systems (GNSS) signals by increasing the background noise. Such space weather events can consequently decrease the quality of GNSS-based results especially for kinematic high-precision positioning. Although solar observatories monitor the solar radio emissions, their direct impacts at the GNSS frequencies are not determined in real-time.
For this purpose, we developed at the Royal Observatory of Belgium (ROB) a method capable to detect SRBs based on real-time C/N0 observations from a regional GNSS (GPS+GLONASS) network. First, S1 and S2 raw data extracted from RINEX files were converted when necessary into the C/N0 unit (dB.Hz) taking into account manufacturer corrections. Then, the differences (∆C/N0) between these C/N0 observables and their medians of the 7 previous satellite ground track repeat cycles, i.e. their normal quiet state, were computed to remove the repeatable patterns (satellite elevation and multipath). Finally, the median <∆C/N0> from the regional GNSS network allows detecting and quantifying the impact of a SRB on GNSS signals quality at each frequency (i.e. L1 and L2).
To validate this method, we investigated the degradation of GPS and GLONASS C/N0 on the entire EUREF Permanent Network (EPN) during 11 intense SRBs occurring between 1999 and 2015. The analysis shows that: (1) GPS and GLONASS ∆C/N0 agree at the 0.1±0.2dB.Hz level; (2) the standard deviation of the <∆C/N0> at L1 and L2 are stable and below 1dB.Hz 96% of the time; the least intense SRB was detected with 1 dB.Hz <∆C/N0> fade and the most intense SRB reached a <∆C/N0> fade of 12 dB.Hz; (3) maximum ∆C/N0 degradation occurs at the maximum solar peak flux delivered by the solar ground observatories; (4) C/N0 degradation becomes larger with increasing solar zenithal angle.
Consequently, the degradation of GNSS signal reception due to SRBs over Europe is now monitored at ROB in near real-time. With this new method, the SRB of the 4th November 2015 was already highlighted at the GNSS L2 frequency. In addition, first results of the method tested into other regions (Africa and South America) using the real-time network of the IGS will be introduced.
|12:30||The Ionospheric Disturbance IndeX (DIX)||Wilken, V et al.||Oral|
| ||Volker Wilken, Martin Kriegel, Norbert Jakowski, Jens Berdermann|
| ||German Aerospace Center (DLR), Institute of Communications and Navigation|
| ||The Ionospheric Disturbance IndeX (DIX)
The ionosphere is the biggest natural error source for all trans-ionospheric signals. Geo-magnetic and
solar indices (e.g. Dst, Kp, ap, F10.7) describe the level of ionospheric disturbance only indirectly and
globally. Industrial customers however ask for a temporally and spatially high resolving ionospheric
disturbance index which properly describes the disturbance level for applications in Global Navigation
Satellite System (GNSS)-Services.
DLR has developed a prototype of an ionospheric Disturbance IndeX (DIX) in the frame of scientific projects.
This index is capable of describing the ionospheric disturbance level with high resolution in space and time.
First attempts to transform the DIX prototype into a standardisable version will be shown.
A standardised DIX may be used for example to compare and evaluate the robustness of different GNSS receiver
facing strong ionospheric disturbances.
|12:45||Improving SBAS navigation performances under severe ionosphere weather conditions||Haddad, F et al.||Oral|
| ||Franck Haddad, Sébastien Trilles|
| ||Thales Alenia Space|
| ||A SBAS (Satellite Based Augmentation System) is a system designed to augment GPS to provide improved precision with an integrity level compatible with aeronautical navigation operations constraints.
The corrections provided by SBAS through geostationary satellite(s) standard broadcast messages are elaborated by computing facilities filled by GPS measurements coming from several stations spread on the desired augmentation service area. For example, EGNOS is the SBAS that provides GPS augmentation services for all Europe (EU28 at least), another SBAS called WAAS does the same for the United States and a part of Canada.
The corrections provided by SBAS are associated to:
- Orbit and Clock estimation of each visible GPS satellite
- Ionosphere delay correction defined through a discrete grid above the area to cover
Nowadays, GPS ephemeris and clock are sufficiently performing by themselves and corrections messages are rather dedicated to ensure integrity in front of potential feared events (measurements corruption due to satellite malfunction, erroneous ephemeris, clock jump, …). It was not the case before year 2000 when GPS measurement were voluntary corrupted by the U.S. to limit GPS performance to several ten meters.
The ionosphere delay is now the main contributor to the GPS positioning error budgets. Indeed, the ionosphere is an ionised medium of the Earth atmosphere that causes non negligible delay on electromagnetic signals like GPS’s. Without correction, the ionosphere delays can deteriorate positioning performance to around 20 meters especially on vertical direction.
In addition, especially on equatorial and polar regions, during high solar activity the ionosphere behaviour (especially during equinoxes) becomes more instable and severe ionosphere delays gradients and scintillation phenomenon occur. High ionosphere gradients challenge SBAS modelling algorithms accuracy and integrity, and ionosphere scintillation provokes measurement loss of lock and several cycle slips on carrier phase measurements causing measurement smoothing algorithms performance degradation.
The purpose of this paper is first to detail the effect of ionosphere on SBAS performance and GPS receivers especially under high ionosphere activity associated with scintillation events. This study will be extended and completed by a focus on equatorial and high latitude areas which undergo extreme ionosphere events. Then, using advanced algorithms designed with ionosphere phenomenon analyses, new SBAS algorithms have been designed to improve ionosphere delay modelling but also to get robust to scintillation events. The achieved performances will be presented, demonstrating the feasibility to meet the APV1 service (precise approach service) 99% availability at least even in presence of scintillation on equatorial regions (worst gradients and scintillation events areas) like in the middle of Africa or in South America.
The results obtained will be based using real data scenarios and possibly completed by simulated data scenarios which present severe ionosphere conditions. Comparisons between current EGNOS CPF algorithms and new algorithms will be performed to appreciate the level of improvement reached.
PostersTuesday November 15, 10:00 - 11:00, Poster Area
|1||Influence of space weather effects on the global and regional ionospheric VTEC-levels ||Hinrichs, J et al.||Invited p-Poster|
| ||Johannes Hinrichs, Volker Bothmer, Niclas Mrotzek, Malte Venzmer, Michael Schmidt, Denise Dettmering, Eren Erdogan, Andreas Goss, Florian Seitz, Klaus Börger, Sylvia Brandert, Barbara Görres, Wilhelm F. Kersten|
| ||Instiute for Astrophysics at the University of Goettingen, Goettingen, Germany; Deutsches Geodätisches Forschungsinstitut der Technischen Universität München (DGFI-TUM), Munich, Germany; German Space Situational Awareness Center (GSSAC), Uedem, Germany; Bundeswehr Geoinformation Center (BGIC), Euskirchen, Germany|
| ||In the German Space Situational Awareness project OPTIMAP (OPerational Tool for Ionosphere Mapping And Prediction), a new forecast service for global ionospheric VTEC maps is currently being developed. Major improvements compared to existing services include the assimilation of different geodetic satellite observations, different mathematical treatments and also the direct use of space weather parameters that influence the ionosphere and their forecasts.
Here we present results from an analysis comparing the effects of different space weather parameters, such as the EUV-flux recorded by SDO, the X-Ray-flux recorded by GOES or the solar wind parameters measured by ACE, to both global and regional VTEC-levels derived from global ionospheric maps. We investigate data over a period of 18 months between November 2014 and April 2016 and compare background level trends and transient events such as flares, geomagnetic storms and quasi-stationary and recurrent features, such as high speed solar wind streams and their associated stream interaction regions.
|2||Estimates of ionospheric higher order effects during quiet and perturbed ionospheric condition||Hoque, M et al.||p-Poster|
| ||M Mainul Hoque, Norbert Jakowski and Jens Berdermann|
| ||German Aerospace Center (DLR), Institute of Communications and Navigation, Kalkhorstweg 53, D-17235 Neustrelitz, Germany|
| ||Ionospheric refraction is considered as one of the major accuracy limiting factors in space-based geodetic techniques such as the GPS, Galileo, GLONASS and Beidou. This is due to the fact that the signals of Global Navigation Satellite Systems (GNSS) are subject to ionospheric refraction and subsequent delays in their travel time. Since the ionosphere is a dispersive medium the first order propagation effect can be removed by transmitting signals at two or multiple frequencies. By combining two or more GNSS signals the major part of the ionospheric propagation delay can be corrected in real time precise positioning by about 99%. However, higher order ionospheric effects such as the second- and third-order terms, effects including ray path bending remain uncorrected in such combinations. The range computation between a satellite and a ground receiver is affected up to several centimeters due to higher order terms and can significantly degrade the accuracy of precise point positioning (PPP) especially during times of high total electron content (TEC). This indicates that the dual-frequency range equation must have additional terms for correcting higher order ionospheric terms.
In our former studies [Hoque and Jakowski 2012, 2008, 2007, 2006] we developed different correction formulas for computing the residual second-, third-order terms and ray path bending related effects in the dual-frequency code-pseudorange and carrier-phase combinations. In the present work we computed their magnitudes using correction formulas in conjunction with slant TECs from worldwide ground GPS data from a quiet and a perturbed ionospheric and geomagnetic activity period of 17 days each (15 - 31 January 2011, 23rd October – 8th November 2011, respectively). The results are compared and conclusions are drawn on the usability of the above mentioned correction models under quiet and perturbed conditions in PPP applications.
MM Hoque, N Jakowski (2012) New correction approaches for mitigating ionospheric higher order effects in GNSS applications, ION GNSS 2012, September 17-21, Nashville Convention Center, Nashville, Tennessee
MM Hoque, N Jakowski (2008) Estimate of higher order ionospheric errors in GNSS positioning, Radio Science. American Geophysical Union. DOI: 10.1029/2007RS003817.
MM Hoque, N Jakowski (2007) Mitigation of higher order ionospheric effects on GNSS users in Europe. GPS Solutions. Springer Berlin / Heidelberg. DOI: 10.1007/s10291-007-0069-5. ISSN 1521-1886.
MM Hoque, N Jakowski (2006) Higher order ionospheric effects in precise GNSS positioning. Journal of Geodesy. Springer Berlin Heidelberg. DOI: 10.1007/s00190-006-0106-0.
|3||Midlatitude Ionospheric density depletion and its impacts on GNSS during geomagnetic storm||Sato, H et al.||p-Poster|
| ||Hiroatsu Sato, Ivan Herrera Pinzon|
| ||German Aerospace Center |
| ||Ionospheric disturbances are the source of degradation of the accuracy of GNSS observables and are especially harmful for multiple GNSS positioning techniques, especially for standalone users. These rapid phenomena are difficult to predict and model, and their impact on the GNSS observables can be most enhanced during large disturbances caused by geomagnetic storms.
During the geomagnetic storm on 17.03.2015, known as St. Patrick’s Day storm, perturbation of geomagnetic fields was observed even in middle latitude in European region. The ground magnetometer chain shows an expansion of disturbance from high to lower latitude in afternoon- evening sectors. When significant disturbance is observed, accompanying plasma density depletions were recorded by GNSS receivers in northeast Germany. The depletions are seen in multiple satellite links where the slant TEC dropped up to 20 TECU. A satellite – receiver link experienced the depletion region for several minutes where the rate of TEC is more irregular than the vicinity. Complementary ground measurements are used to study the origin and dynamics of the depletions.
We also discuss possible indication of this event for GNSS applications such as positioning and navigation. The rate of TEC, which is proportional to rate of ionospheric delay, can be used an indicator for the characterisation of the system's operation and the real-time detection of threats in relation to ionospheric events. The relevance of this indicator and the use of sufficient thresholds differing between nominal and perturbed behavior during GNSS disturbance, to enable the differentiation between usable/unusable observations for positioning will be presented.
|4||Ground-based measurements of ionospheric dynamics||Kouba, D et al.||p-Poster|
| ||Daniel Kouba, Jaroslav Chum|
| ||Institute of Atmospheric Physics, Czech Academy of Sciences|
| ||The oldest and still used ground-based ionospheric monitoring is vertical ionospheric sounding. It is carried out routinely on many ionospheric stations around the world. Vertical ionospheric sounding produces ionograms and subsequently electron density profiles. However, modern ionosondes are also able to monitor dynamics of ionospheric layers. Measurements of plasma motion bring an important information about the state of the ionosphere.
For more than ten years we have been providing routine Digisonde Drift Measurements for both E and F regions in addition to a regular ionogram sounding at ionospheric observatory Pruhonice. This measurement is performed with 15 minutes cadence as in the case of ionograms.
Since 2007 we have also been providing Continuous Doppler Sounding measurement in the Czech Republic. Currently this measurement uses three sounding frequencies that cover E and F ionospheric layers. Continuous Doppler Sounding measurement allows monitoring of wave processes in the ionosphere with time resolution of around 10 s.
Both Digisonde and Continuous Doppler sounder measure about the same volume in the ionosphere, which makes it possible to compare and complement measurements performed by these two instruments.
Our contribution compares the potential of both measurements to investigate dynamics of the ionosphere. Several case studies are presented. Monitoring of the dynamics of the ionosphere has great potential for the prediction of ionospheric conditions.|
|5||The Impact of the Thermosphere on Plasma Structures in the High-Latitude Ionosphere||Wood, A et al.||p-Poster|
| ||Amy Ronksley, Alan Wood and Anasuya Aruliah|
| ||School of Science and Technology, Nottingham Trent University, Nottingham, UK; Atmospheric Physics Laboratory, Astrophysics Department, University College London, London, UK.|
| ||Plasma structures in the ionosphere can disrupt trans-ionospheric radio signals, such as those used by the Global Navigation Satellite Systems (GNSS). Large-scale structures (10-100s km across) are associated with small-scale structures. These large-scale structures are known to be dependent on UT, season, solar cycle, geomagnetic activity, solar wind conditions and location. The dependence of these structures on the thermosphere has never been fully established, despite the well-understood ionosphere-thermosphere coupling mechanism. The thermosphere is a key parameter in the Joule heating equation. It influences the vertical dynamics of the atmosphere which, in turn, alters the density profile of the thermosphere and hence the lifetime of the plasma density structures. Only recently has the high temporal (few minutes) and spatial (100km) scales of variability of the thermosphere been established.
Ionospheric measurements from the EISCAT (European Incoherent Scatter) Svalbard Radar and thermospheric measurements from the UCL Fabry Perot Interferometers have been compared across a solar cycle and the statistical relationship between these parameters has been determined. The thermospheric parameters can be added to a model to predict the amount of plasma structuring in the ionosphere and the steps required to implement this are discussed.|
|6||Space Weather effects on GNSS and precise positioning ||Aa, E et al.||p-Poster|
| ||Ercha Aa, Siqing Liu, and Wengeng Huang|
| ||National Space Science Center, Chinese Academy of Sciences|
| ||In this study, a regional 3-D ionospheric electron density specification over China and adjacent areas (70E-140E in longitude, 15N-55N in latitude, and 100-900 km in altitude) is developed on the basis of data assimilation technique. The International Reference Ionosphere (IRI) is used as a background model, and a three-dimensional variational technique is used to assimilate both the ground-based Global Navigation Satellite System (GNSS) observations from the Crustal Movement Observation Network of China (CMONOC) and International GNSS Service (IGS) and the ionospheric radio occultation (RO) data from FORMOSAT-3/COSMIC (F3/C) satellites. The regional 3-D gridded ionospheric electron densities can be generated with temporal resolution of 5 min in universal time, horizontal resolution of 2 degree in latitude and longitude, and vertical resolution of 20 km between 100 and 500 km and 50 km between 500 and 900 km. The data assimilation results are validated through extensive comparison with several sources of electron density information, including (1) ionospheric total electron content (TEC); (2) Abel-retrieved F3/C electron density profiles (EDPs); (3) ionosonde foF2 and bottomside EDPs; and (4) the Utah State University Global Assimilation of Ionospheric Measurements (USU-GAIM) under both geomagnetic quiet and disturbed conditions. The validation results show that the data assimilation procedure pushes the climatological IRI model toward the observation, and a general accuracy improvement of 15-30% can be expected. The comparisons also indicate that the data assimilation results are more close to the Center for Orbit Determination of Europe (CODE) TEC and Madrigal TEC products than USU-GAIM. These initial results might demonstrate the effectiveness of the data assimilation technique in improving specification of local ionospheric morphology.||