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Multi-satellite based possible precursory signals detection linked to the 2024 Mw 7.5 Noto Peninsula Japan earthquake
(2025-06-15)
Shahzad, Rasim
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Shah, Munawar
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Nabi, Imtiaz
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Jamjareegulgarn, Punyawi
Satellite-based anomaly detection can provide substantial precursory information linked to impending earthquakes (EQ). The strong EQs are followed by some complex precursory signals both before and after the main shock. For this, different methods and datasets are employed to monitor these disastrous events. In our study, we used the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite to evaluate land surface temperature (LST), the Global Navigation Satellite System (GNSS) to observe total electron content (TEC) variations, Swarm satellites to monitor spatial variations in electron density, and Cosmic satellites were used to measure variations in the vertical profile of electron density to look for the complex precursors of Noto Peninsula Japan EQ of 7.5 Mw (occurred on 1st January 2024). Our objective was to observe both the pre- and post-EQ induced anomalies within 25 days and 10 days of the main shock by integrating the statistical, nonlinear autoregressive network with exogenous inputs (NARX) and continuous wavelet transformation (CWT) methods. We found synchronized and co-located pre-seismic anomalies on December 25 in LST, TEC and electron density. Which was further confirmed using NARX and CWT as well. Additionally, we found some potential post-seismic anomalies. There was an anomalous enhancement in daytime LST, TEC, and electron density on January 2nd with the exception of nighttime LST which showed abrupt increments on the night of the main shock (i.e., January 1st). These findings point towards the strong EQ-induced energy into the atmosphere and ionosphere for more prominent proof of lithosphere-atmosphere–ionosphere coupling (LAIC).
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Variations in Ionospheric Total Electron Content and Scintillation at GPS stations in Uzbekistan and China during the Annular Solar Eclipse on June 21, 2020
(2025-05-01)
Eshkuvatov, H. E.
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Jamjareegulgarn, Punyawi
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Ahmedov, B. J.
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Tillayev, Y. A.
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Ruziev, Z. J.
This study presents a novel investigation into the distinct ionospheric variations observed over China and Uzbekistan during the annular solar eclipse on June 21, 2020. For the first time, we demonstrate the influence of this celestial event on Total Electron Content (TEC) measurements obtained from GPS satellites. We analyzed fluctuations in TEC and the Ionospheric Scintillation Index (S4) across six strategically selected sites—three in Uzbekistan (MTAL, KIT3, MADK) and three in China (JFNG, LHAZ, BJFS) located near the eclipse path, with obscuration levels of 52%, 57%, 58%, in Uzbekistan and 92%, 94% and 95% in China. Our study involved continuous monitoring of ionospheric parameters over three days, from June 20 to June 22, 2020. Results indicated a significant TEC depletion ranging from 10% to 30% on the day of the eclipse. The analysis reveals that both TEC levels and the S4 scintillation index experienced notable reductions during the event, attributed to the decreased ionizing radiation. These findings enhance our understanding of ionospheric dynamics in response to solar eclipses and have important implications for satellite communication and navigation systems.
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The study on the relationship between ionospheric delay and low-cost localizing robots
(2025-03-01)
Sumniang, Patiphan
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Sittichai, Wishapol
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Kenpankho, Prasert
The dispersive and anisotropic nature of the ionosphere above certain regions particularly on Thailand's low − nearly equatorial − latitude, positioning accuracy is seriously affected when using a precision limited model. Change in ionospheric delay is a key factor impacting the Global Navigation Satellite Systems (GNSS) positioning and navigation accuracy. We studied the effect of ionospheric delay on localizing low-cost robots. We investigated the positioning error using ionospheric delay from a GNSS receiver, IRI and our campus, KMITL, in Bangkok, to guide our ‘G-LOC’ robot. There were eight target points, set from 3 to 50 m at the same meridian with varying latitudes. Impacts on a robot moving on low solar activity days, high solar activity days, daytime, and nighttime were measured over 12 months in 2023. We found that high solar activity day impacts a robot moving on highest accuracy error up to 363 cm at high speed. In addition, we found that daytime impacts a robot moving on highest accuracy error up to 154.05 cm at high speed as well. Ionospheric delay according to high and low solar activities, and daytime, and nighttime effects on the GNSS interference transmitted to a low-cost localizing robot was expected to affect moving errors, but it did not seem to lead to a significant difference in error between the low and high solar activity days.
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Global Navigation Satellite System (GNSS) Low-Cost Robotics Platform for Competition Game
(2025-01-01)
Sumniang, Patiphan
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Putthong, Burin
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Namniwong, Thapanan
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Kenpankho, Prasert
In this research, the Global Navigation Satellite System (GNSS) low-cost robotics platform for competition game was designed, including the development of competition rules and field. The competition rules are specifically tailored to GNSS low-cost robot, highlighting the essential components required to build robots based on GNSS low-cost robotic platform. This research aims to promote learning and skill development in robots and GNSS, with a focus on affordable resources to ensure accessibility for students and independent developers. In research methodology, a total of 58 teams with 116 participants took part in the GNSS low-cost robotics platform competition game, including 47 high school level teams (94 participants), 6 vocational level teams (12 participants), and five undergraduate level teams (1 0 participants). As the results, the competition game was successfully developed by the GNSS low-cost robotic platform, with over 70% of participants demonstrating a solid understanding of GNSS navigation, robot, and game design. Participants rated innovation-focused activities highly (4.55), highlighting the competition game role in inspiring creativity in GNSS and low-cost robot. In term of rule for competition game, participants gave the rates on fairness (4.23) and consistency (4.28) which were well received, although rule clarity received the lowest score (3.84), suggesting the need for clearer guidelines. In addition, the pre- and posttest assessments on participants' knowledge, understanding, and inspiration in GNSS navigation, robot, and game design, further confirmed the effectiveness of GNSS low-cost robotics platform competition game by giving the improved mean score from 23.06 to 27.01.
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Compatibility of Low-Cost GNSS Receivers for Total Electron Content (TEC) Analysis
(2025-01-01)
Rana, Bhim Bahadur
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Supnithi, Pornchai
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Myint, Lin M.M.
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Tongkasem, Napat
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Budtho, Jirapoom
Although the geodetic GNSS receivers are highly precise, they are inaccessible to every user, especially in remote areas. Therefore, this work aimed to find the reasons that bolster the low-cost GNSS receivers to be used with high resolution over a wide area, instead of geodetic in space weather studies. A comparative analysis was conducted between a low-cost Ublox ZED-F9P GNSS receiver and a geodetic Novatel Propak6 GNSS receiver, focusing on ionospheric parameters such as slant total electron content (STEC), vertical total electron content (VTEC), and the number of satellites tracked using the Global Positioning System (GPS). Additionally, VTEC values were compared with the GIM model. Both receivers exhibited a similar pattern of TEC, with the R2 value of 0.9734 and the root mean square error of 3.4583. The number of satellites tracked by both receivers during the observed periods was also found to be similar. Moreover, the VTEC results obtained from the low-cost GNSS receiver showed compatibility with the GIM model, demonstrating the reliability of the low-cost receiver in comparison to the geodetic GNSS receiver.
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The Study of the Rate of TEC Index over Thailand
(2025-01-01)
Buakao, Nitipat
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Phothila, Prarinya
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Kenpankho, Prasert
This study examines the variations in Rate of TEC Index (ROTI) across three provinces in Thailand-Bangkok, Chiang Mai, and Chumphon-using Total Electron Content (TEC) data derived from BG2s GPS receivers during the period from January to March 2025. ROTI values were classified into three levels: high (>0.8), moderate (0.4-0.8), and low (<0.4) TEC variability. The analysis revealed that Chumphon exhibited the highest TEC variability, followed by Bangkok and Chiang Mai. In January, Bangkok recorded elevated ROTI values between 14:25 and 15:25 local time, with lower values observed from midnight to noon and after sunset. In February, ROTI values exceeding 0.8 were detected between 13:00 and 20:00, with Chumphon showing the most intense fluctuations. In March, high ROTI values occurred from 13:00 to 22:00, with Bangkok experiencing the most prolonged periods of TEC disturbance. These results underscore the spatial and temporal dynamics of ionospheric irregularities in low-latitude regions and support the effectiveness of ROTI as a diagnostic tool for monitoring space weather impacts on GNSS signals.
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Local mitigation of higher-order ionospheric effects in DFMC SBAS and system performance evaluation
(2024-04-01)
Sophan, Somkit
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Supnithi, Pornchai
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Myint, Lin M.M.
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Saito, Susumu
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Hozumi, Kornyanat
Dual-frequency multi-constellation (DFMC) satellite-based augmentation system (SBAS) is a new SBAS standard for aeronautical navigation systems. It supports aircraft navigation from the enroute to approach phases via the L1 and L5 frequencies (1575.42 and 1176.45 MHz). Although the ionosphere-free (IF) combination in the DFMC SBAS operation removes the first-order ionospheric delays in the pseudorange measurement, remaining terms including the satellite-clock offset errors and higher-order ionospheric (HOI) delays are still unaccounted for. The DFMC SBAS accuracy and integrity can be affected by the HOI effects, especially during severe ionospheric disturbances. In this work, we present the local DFMC SBAS corrections with and without the mitigation of HOI delays. We first estimate the HOI delay terms using the received pseudorange followed by separate satellite and receiver bias estimations based on the minimum sum-variance technique. The integrity terms can then be obtained. The performances of DFMC SBAS using the global navigation satellite system (GNSS) data including GPS, Galileo, and QZSS are evaluated using obtained GNSS data at stations in Thailand on the ionospheric quiet and disturbed days. The results show that with the HOI mitigation, the vertical positioning errors (VPE) on the quiet and disturbed days can be improved by 12% and 9%, whereas the vertical protection levels (VPL) are improved by 16% and 21%, respectively. In addition, we perform a preliminary assessment of DFMC SBAS based on the International Civil Aviation Organization (ICAO) requirements of two categories: Localizer Performance with Vertical guidance (LPV-200) and Category I precision approach (CAT-I) showing promising results.
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Investigations of User Positioning Errors by Using Local DFMC SBAS Correction with Higher-Order Ionospheric Delay Mitigation in Thailand
(2024-01-01)
Sophan, Somkit
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Supnithi, Pornchai
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Myint, Lin M.M.
Dual-frequency multi-constellation (DFMC) satellite-based augmentation system (SBAS) is essential to support airplane navigation. Typically, the global navigation satellite system (GNSS) with the L1 (1575.42 MHz) and L5 (1176.45 MHz) frequencies are utilized to remove the ionospheric delays based on the ionosphere-free (IF) combination (L1-L5), nevertheless, the errors due to higher-order ionospheric (HOI) delays still need to be corrected. With the local DFMC SBAS correction with a HOI mitigation in Thailand had not been considered and investigated yet. Therefore, we investigate local DFMC SBAS corrections with the HOI mitigation which are generated from the base stations in Thailand. The corrections are approximated from the local total electron content (TEC) values based on the Klobuchar model. Firstly, the local HOI days are estimated by using the observed pseudorange, and consequently, the local DFMC SBAS corrections are generated based on the minimum sum-variance technique with the IF carrier smoothing code. The GPS, Galileo, and QZSS data from the reference stations network in Thailand are utilized. In the preliminary study, the user positioning errors on the quiet days are evaluated based on the single point positioning (SPP) algorithm. The results show that both horizontal and vertical position errors are reduced by the local DFMC SBAS corrections with the HOI mitigation. The position error improvements on the quiet days can be experienced by 11%.
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Analysis of Cybersecurity Vulnerabilities in Maritime GNSS Systems
(2024-01-01)
Chinnarong, Thirawat
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Pomsathit, Auttapon
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Yongsiriwit, Karn
The maritime industry is increasingly dependent on Global Navigation Satellite Systems (GNSS) such as GPS, GLONASS, BeiDou, and Galileo for navigation and operational efficiency. However, these systems are vulnerable to cyber threats like spoofing and jamming, which can severely disrupt maritime operations by misleading navigation systems [1], [2]. This study analyzes the cybersecurity vulnerabilities of GNSS systems used in maritime environments, utilizing a Software-Defined Radio (SDR) to simulate GNSS spoofing attacks on various maritime GNSS receivers [3]. The findings reveal that all tested receivers are susceptible to spoofing attacks, underscoring the need for enhanced cybersecurity measures [4]. The study advocates for the development of advanced detection systems, improved signal authentication, and adherence to cybersecurity guidelines provided by organizations such as INTERTANKO and the International Maritime Organization (IMO) [5], [6]. The proposed strategies aim to mitigate the risks associated with GNSS vulnerabilities and ensure the safety and security of maritime operations.
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Applicability of Klobuchar Model for STEC Estimation Over Thailand Region
(2023-01-01)
Srisamoodkham, Worachai
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Ansari, Kutubuddin
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Jamjareegulgarn, Punyawi
In the current study, we investigated the total electron content (TEC) variations over Thailand region by using five multi-constellation Global Navigation satellite system (GNSS) signals. The STEC variations for all multiple GNSSs were computed with well-known ionospheric Klobuchar model and compared with the STEC values of Global Ionospheric map (GIM) on a storm day (May 12, 2021), before as well as after this storm day. The results showed that most of the GIM STEC values (GSVs) were overestimated with the Klobuchar model STEC values (KMSVs) for all constellations, except QZSS. As for the QZSS, the KMSVs were closest to the GSVs. Likewise, the MS-SHF-based Klobuchar model (MSSHFKM method) was able to compensate the ionospheric delay effectively as compared to the original Klobuchar model up to 77.08% RMSE during the geomagnetic storm on May 12, 2021.

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