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Space Geodesy and Ionosphere

A special issue of Remote Sensing (ISSN 2072-4292).

Deadline for manuscript submissions: closed (10 May 2022) | Viewed by 22311

Special Issue Editors


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Guest Editor
Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, 00143 Rome, Italy
Interests: ionosphere; ionosonde data; space weather services

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Guest Editor
Istituto Nazionale di Vulcanologia, Via di Vigna Murata 605, 00143 Rome, Italy
Interests: geodesy; geophysics; sea level; geosciences
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Global Navigation Satellite System (GNSS) networks for monitoring the ground deformations of tectonic and volcanic areas and sea-level research have dramatically progressed worldwide during the last two decades. The data provided by GNSS networks improved our knowledge of the processes of the accumulation and release of deformation during the seismic cycle and the preparatory phase of volcanic eruptions. High-rate GNSS data are used to measure the high-frequency ground movements during earthquakes. In combination with tide gauges, GNSS data can reveal the contribution of vertical land movements to local sea level trends. In topography, GNSS stations are reference for real time applications, like aerial photogrammetry or hydrographic surveys.

Apart from the geodetic and topographic applications for solid earth, the data provided by such networks can be used to obtain ionospheric Total Electron Content (TEC) maps. These maps are useful to support both high-frequency (HF) radio communications and GNSS users. They can also be used to study the ionosphere morphology and dynamics during strong space weather events. For example, TEC mapping has shown great capability in capturing the evolution of Storm-Enhanced Density (SED) and the significant TEC gradients it creates. These phenomena may be quite complicated, both physically and from the point of view of their spatial/temporal evolution. The very fine spatial resolution of the maps helps to resolve global large‐scale ionospheric disturbance down to very small spatial and temporal scales during storm events.

The aim of this Special Issue is to show how precise positioning is affected by space weather events in static and kinematic geodetic applications and how the most recent techniques of analysis can mitigate this effect, leading to new findings related to the ionosphere.

Dr. Carlo Scotto
Dr. Marco Anzidei
Guest Editors

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • TEC maps
  • precise positioning
  • geodesy
  • topography
  • earthquakes
  • ionosphere
  • space weather

Published Papers (7 papers)

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25 pages, 13787 KiB  
Article
Spatial and Temporal Distributions of Ionospheric Irregularities Derived from Regional and Global ROTI Maps
by Chinh Thai Nguyen, Seun Temitope Oluwadare, Nhung Thi Le, Mahdi Alizadeh, Jens Wickert and Harald Schuh
Remote Sens. 2022, 14(1), 10; https://doi.org/10.3390/rs14010010 - 21 Dec 2021
Cited by 11 | Viewed by 4043
Abstract
Major advancements in the monitoring of both the occurrence and impacts of space weather can be made by evaluating the occurrence and distribution of ionospheric disturbances. Previous studies have shown that the fluctuations in total electron content (TEC) values estimated from Global Navigation [...] Read more.
Major advancements in the monitoring of both the occurrence and impacts of space weather can be made by evaluating the occurrence and distribution of ionospheric disturbances. Previous studies have shown that the fluctuations in total electron content (TEC) values estimated from Global Navigation Satellite System (GNSS) observations clearly exhibit the intensity levels of ionospheric irregularities, which vary continuously in both time and space. The duration and intensity of perturbations depend on the geographic location. They are also dependent on the physical activities of the Sun, the Earth’s magnetic activities, as well as the process of transferring energy from the Sun to the Earth. The aim of this study is to establish ionospheric irregularity maps using ROTI (rate of TEC index) values derived from conventional dual-frequency GNSS measurements (30-s interval). The research areas are located in Southeast Asia (15°S–25°N latitude and 95°E–115°E longitude), which is heavily affected by ionospheric scintillations, as well as in other regions around the globe. The regional ROTI map of Southeast Asia clearly indicates that ionospheric disturbances in this region are dominantly concentrated around the two equatorial ionization anomaly (EIA) crests, occurring mainly during the evening hours. Meanwhile, the global ROTI maps reveal the spatial and temporal distributions of ionospheric scintillations. Within the equatorial region, South America is the most vulnerable area (22.6% of total irregularities), followed by West Africa (8.2%), Southeast Asia (4.7%), East Africa (4.1%), the Pacific (3.8%), and South Asia (2.3%). The generated maps show that the scintillation occurrence is low in the mid-latitude areas during the last solar cycle. In the polar regions, ionospheric irregularities occur at any time of the day. To compare ionospheric disturbances between regions, the Earth is divided into ten sectors and their irregularity coefficients are calculated accordingly. The quantification of the degrees of disturbance reveals that about 58 times more ionospheric irregularities are observed in South America than in the southern mid-latitudes (least affected region). The irregularity coefficients in order from largest to smallest are as follows: South America, 3.49; the Arctic, 1.94; West Africa, 1.77; Southeast Asia, 1.27; South Asia, 1.24; the Antarctic, 1.10; East Africa, 0.89; the Pacific, 0.32; northern mid-latitudes, 0.15; southern mid-latitudes, 0.06. Full article
(This article belongs to the Special Issue Space Geodesy and Ionosphere)
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18 pages, 6538 KiB  
Article
HF-Induced Modifications of the Electron Density Profile in the Earth’s Ionosphere Using the Pump Frequencies near the Fourth Electron Gyroharmonic
by Alexey V. Shindin, Evgeny N. Sergeev, Savely M. Grach, Gennady M. Milikh, Paul Bernhardt, Carl Siefring, Michael J. McCarrick and Yulia K. Legostaeva
Remote Sens. 2021, 13(23), 4895; https://doi.org/10.3390/rs13234895 - 2 Dec 2021
Cited by 2 | Viewed by 1497
Abstract
We discuss results on plasma density profile modifications in the F-region ionosphere that are caused by HF heating with the frequency f0 in the range [(−150 kHz)–(+75 kHz)] around the fourth electron gyroharmonic 4fc. The experiments were conducted at [...] Read more.
We discuss results on plasma density profile modifications in the F-region ionosphere that are caused by HF heating with the frequency f0 in the range [(−150 kHz)–(+75 kHz)] around the fourth electron gyroharmonic 4fc. The experiments were conducted at the HAARP facility in June 2014. A multi-frequency Doppler sounder (MDS), which measures the phase and amplitude of reflected sounding radio waves, complemented by the observations of the stimulated electromagnetic emission (SEE) were used for the diagnostics of the plasma perturbations. We detected noticeable plasma expulsion from the reflection region of the pumping wave and from the upper hybrid region, where the expulsion from the latter was strongly suppressed for f0 ≈ 4fc. The plasma expulsion from the upper hybrid region was accompanied by the sounding wave’s anomalous absorption (AA) slower development for f0 ≈ 4fc. Furthermore, slower development and weaker expulsion were detected for the height region between the pump wave reflection and upper hybrid altitudes. The combined MDS and SEE allowed for establishing an interconnection between different manifestations of the HF-induced ionospheric turbulence and determining the altitude of the most effective pump wave energy input to ionospheric plasma by using the dependence on the offset between f0 and 4fc. Full article
(This article belongs to the Special Issue Space Geodesy and Ionosphere)
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21 pages, 6301 KiB  
Article
IONORING: Real-Time Monitoring of the Total Electron Content over Italy
by Claudio Cesaroni, Luca Spogli and Giorgiana De Franceschi
Remote Sens. 2021, 13(16), 3290; https://doi.org/10.3390/rs13163290 - 19 Aug 2021
Cited by 14 | Viewed by 2486
Abstract
IONORING (IONOspheric RING) is a tool capable to provide the real-time monitoring and modeling of the ionospheric Total Electron Content (TEC) over Italy, in the latitudinal and longitudinal ranges of 35°N–48°N and 5°E–20°E, respectively. IONORING exploits the Global Navigation Satellite System (GNSS) data [...] Read more.
IONORING (IONOspheric RING) is a tool capable to provide the real-time monitoring and modeling of the ionospheric Total Electron Content (TEC) over Italy, in the latitudinal and longitudinal ranges of 35°N–48°N and 5°E–20°E, respectively. IONORING exploits the Global Navigation Satellite System (GNSS) data acquired by the RING (Rete Integrata Nazionale GNSS) network, managed by the Istituto Nazionale di Geofisica e Vulcanologia (INGV). The system provides TEC real-time maps with a very fine spatial resolution (0.1° latitude x 0.1° longitude), with a refresh time of 10 min and a typical latency below the minute. The TEC estimated at the ionospheric piercing points from about 40 RING stations, equally distributed over the Italian territory, are interpolated using locally (weighted) regression scatter plot smoothing (LOWESS). The validation is performed by comparing the IONORING TEC maps (in real-time) with independent products: (i) the Global Ionospheric Maps (GIM) - final product- provided by the International GNSS Service (IGS), and (ii) the European TEC maps from the Royal Observatory of Belgium. The validation results are satisfactory in terms of Root Mean Square Error (RMSE) between 2 and 3 TECu for both comparisons. The potential of IONORING in depicting the TEC daily and seasonal variations is analyzed over 3 years, from May 2017 to April 2020, as well as its capability to account for the effect of the disturbed geospace on the ionosphere at mid-latitudes. The IONORING response to the X9.3 flare event of September 2017 highlights a sudden TEC increase over Italy of about 20%, with a small, expected dependence on the latitude, i.e., on the distance from the subsolar point. Subsequent large regional TEC various were observed in response to related follow-on geomagnetic storms. This storm is also used as a case event to demonstrate the potential of IONORING in improving the accuracy of the GNSS Single Point Positioning. By processing data in kinematic mode and by using the Klobuchar as the model to provide the ionospheric correction, the resulting Horizontal Positioning Error is 4.3 m, lowering to, 3.84 m when GIM maps are used. If IONORING maps are used as the reference ionosphere, the error is as low as 2.5 m. Real-times application and services in which IONORING is currently integrated are also described in the conclusive remarks. Full article
(This article belongs to the Special Issue Space Geodesy and Ionosphere)
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22 pages, 12670 KiB  
Article
Occurrence of GPS Loss of Lock Based on a Swarm Half-Solar Cycle Dataset and Its Relation to the Background Ionosphere
by Michael Pezzopane, Alessio Pignalberi, Igino Coco, Giuseppe Consolini, Paola De Michelis, Fabio Giannattasio, Maria Federica Marcucci and Roberta Tozzi
Remote Sens. 2021, 13(11), 2209; https://doi.org/10.3390/rs13112209 - 4 Jun 2021
Cited by 10 | Viewed by 3294
Abstract
This paper discusses the occurrence of Global Positioning System (GPS) loss of lock events obtained by considering total electron content (TEC) measurements carried out by the three satellites of the European Space Agency Swarm constellation from December 2013 to December 2020, which represents [...] Read more.
This paper discusses the occurrence of Global Positioning System (GPS) loss of lock events obtained by considering total electron content (TEC) measurements carried out by the three satellites of the European Space Agency Swarm constellation from December 2013 to December 2020, which represents the longest dataset ever used to perform such an analysis. After describing the approach used to classify a GPS loss of lock, the corresponding occurrence is analyzed as a function of latitude, local time, season, and solar activity to identify well-defined patterns. Moreover, the strict relation of the occurrence of the GPS loss of lock events with defined values of both the rate of change of electron density index (RODI) and the rate of change of TEC index (ROTI) is highlighted. The scope of this study is, on one hand, to characterize the background conditions of the ionosphere for such events and, on the other hand, to pave the way for their possible future modeling. The results shown, especially the fact that GPS loss of lock events tend to happen for well-defined values of both RODI and ROTI, are of utmost importance in the light of Space Weather effects mitigation. Full article
(This article belongs to the Special Issue Space Geodesy and Ionosphere)
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19 pages, 4805 KiB  
Article
Performance Evaluation of VTEC GIMs for Regional Applications during Different Solar Activity Periods, Using RING TEC Values
by Vincenza Tornatore, Claudio Cesaroni, Michael Pezzopane, Mohamad Mahdi Alizadeh and Harald Schuh
Remote Sens. 2021, 13(8), 1470; https://doi.org/10.3390/rs13081470 - 10 Apr 2021
Cited by 12 | Viewed by 1972
Abstract
This paper presents a comparison of the vertical total electron content (vTEC) estimated over Italy using two different approaches: the GPS Global Ionosphere Maps (GIMs) and the so-called “calibration technique” developed by Ciraolo in 2007. The study has been carried out at a [...] Read more.
This paper presents a comparison of the vertical total electron content (vTEC) estimated over Italy using two different approaches: the GPS Global Ionosphere Maps (GIMs) and the so-called “calibration technique” developed by Ciraolo in 2007. The study has been carried out at a regional level by considering three Italian dual-frequency stations of the GPS permanent network “Rete Integrata Nazionale GPS (RING)”. The GPS receivers are permanently installed at Madesimo (geographical coordinates: 46.5 N, 9.4 E), Rome (geographical coordinates: 41.8 N, 12.5 E) and Resuttano (geographical coordinates: 37.7 N, 14.1 E), respectively in the north, center and south of Italy. Time windows selected for the analysis include periods of both low (July 2008 to June 2009) and high (September 2013 to August 2014) solar activity. The two datasets have also been studied considering both quiet and disturbed geomagnetic activity conditions. Moreover, the effects of an extreme geomagnetic storm have been investigated in March 2015 when the well-known St. Patrick storm occurred. Overall, GIM estimated values are always higher than those calibrated by the Ciraolo procedure for all the considered datasets. The differences between the two methods increase as the latitude decreases, and they increase as the solar activity intensifies. The outcomes of this study shall be helpful when applying GlMs at a regional level. Full article
(This article belongs to the Special Issue Space Geodesy and Ionosphere)
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19 pages, 3594 KiB  
Article
High-Resolution Ionosphere Corrections for Single-Frequency Positioning
by Andreas Goss, Manuel Hernández-Pajares, Michael Schmidt, David Roma-Dollase, Eren Erdogan and Florian Seitz
Remote Sens. 2021, 13(1), 12; https://doi.org/10.3390/rs13010012 - 22 Dec 2020
Cited by 12 | Viewed by 2976
Abstract
The ionosphere is one of the main error sources in positioning and navigation; thus, information about the ionosphere is mandatory for precise modern Global Navigation Satellite System (GNSS) applications. The International GNSS Service (IGS) and its Ionosphere Associated Analysis Centers (IAAC) routinely provide [...] Read more.
The ionosphere is one of the main error sources in positioning and navigation; thus, information about the ionosphere is mandatory for precise modern Global Navigation Satellite System (GNSS) applications. The International GNSS Service (IGS) and its Ionosphere Associated Analysis Centers (IAAC) routinely provide ionospheric information in terms of global ionosphere maps (final GIM). Typically, these products are modeled using series expansion in terms of spherical harmonics (SHs) with a maximum degree of n=15 and are based on post processed observations from Global Navigation Satellite Systems (GNSS), as well as final satellite orbits. However, precise applications such as autonomous driving or precision agriculture require real-time (RT) information about the ionospheric electron content with high spectral and spatial resolution. Ionospheric RT-GIMs are disseminated via Ntrip protocol using the SSR VTEC message of the RTCM. This message can be streamed in RT, but it is limited for the dissemination of coefficients of SHs of lower degrees only. It allows the dissemination of SH coefficients up to a degree of n=16. This suits to most the SH models of the IAACs, but higher spectral degrees or models in terms of B-spline basis functions, voxels, splines and many more cannot be considered. In addition to the SHs, several alternative approaches, e.g., B-splines or Voxels, have proven to be appropriate basis functions for modeling the ionosphere with an enhanced resolution. Providing them using the SSR VTEC message requires a transfer to SHs. In this context, the following questions are discussed based on data of a B-spline model with high spectral resolution; (1) How can the B-spline model be transformed to SHs in order to fit to the RTCM requirements and (2) what is the loss of detail when the B-spline model is converted to SHs of degree of n=16? Furthermore, we discuss (3) what is the maximum necessary SH degree n to convert the given B-spline model and (4) how can the transformation be performed to make it applicable for real-time applications? For a final assessment, we perform both, the dSTEC analysis and a single-frequency positioning in kinematic mode, using the transformed GIMs for correcting the ionospheric delay. The assessment shows that the converted GIMs with degrees n30 coincide with the original B-spline model and improve the positioning accuracy significantly. Full article
(This article belongs to the Special Issue Space Geodesy and Ionosphere)
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21 pages, 3139 KiB  
Technical Note
Effects of the 12 May 2021 Geomagnetic Storm on Georeferencing Precision
by Juan Carlos Valdés-Abreu, Marcos A. Díaz, Juan Carlos Báez and Yohadne Stable-Sánchez
Remote Sens. 2022, 14(1), 38; https://doi.org/10.3390/rs14010038 - 23 Dec 2021
Cited by 9 | Viewed by 3843
Abstract
In this work, we present the positioning error analysis of the 12 May 2021 moderate geomagnetic storm. The storm happened during spring in the northern hemisphere (fall in the south). We selected 868 GNSS stations around the globe to study the ionospheric and [...] Read more.
In this work, we present the positioning error analysis of the 12 May 2021 moderate geomagnetic storm. The storm happened during spring in the northern hemisphere (fall in the south). We selected 868 GNSS stations around the globe to study the ionospheric and the apparent position variations. We compared the day of the storm with the three previous days. The analysis shows the global impact of the storm. In the quiet days, 93% of the stations had 3D errors less than 10 cm, while during the storm, only 41% kept this level of accuracy. The higher impact was over the Up component. Although the stations have algorithms to correct ionospheric disturbances, the inaccuracies lasted for nine hours. The most severe effects on the positioning errors were noticed in the South American sector. More than 60% of the perturbed stations were located in this region. We also studied the effects produced by two other similar geomagnetic storms that occurred on 27 March 2017 and on 5 August 2019. The comparison of the storms shows that the effects on position inaccuracies are not directly deductible neither from the characteristics of geomagnetic storms nor from enhancement and/or variations of the ionospheric plasma. Full article
(This article belongs to the Special Issue Space Geodesy and Ionosphere)
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