Budtho, Jirapoom

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Budtho, Jirapoom
Alternative Name
Budtho, J.
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Email
jirapoom.bu@kmitl.ac.th

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    Compatibility of Low-Cost GNSS Receivers for Total Electron Content (TEC) Analysis
    (2025-01-01)
    Rana, Bhim Bahadur
    ;
    Supnithi, Pornchai
    ;
    Myint, Lin M.M.
    ;
    Tongkasem, Napat
    ;
    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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    Radio Frequency Interference (RFI) Analysis on GNSS Signals and Effects on Positioning Errors
    (2024-01-01)
    Sophan, Somkit
    ;
    Supnithi, Pornchai
    ;
    Myint, Lin M.M.
    ;
    Budtho, Jirapoom
    ;
    Saito, Susumu
    Radio frequency interference (RFI) frequently exists in the Global Navigation Satellite System (GNSS) signals. Conventionally, the monitoring of carrier-to-noise density ratio (C/N0) values can be used to detect the RFI levels. Since RFI affects the quality of GNSS signals and applications, we determine three RFI levels (low, moderate, and high) based on C/N0 then statistically analyze the RFI occurrences in Bangkok, Thailand. The percentage of RFI occurrences is computed based on the average C/N0 technique. We compare the RFI occurrence statistics of 2 GNSS stations in the urban (DPT9) and suburban (KMIT) areas in Bangkok in June 2021 (COVID-19 lockdown period) and 2023 (Post COVID-19 period). The results show that during the COVID-19 period, the RFI occurrences are much reduced at the DPT9 station in the center of the city. The high (severe) RFI levels at DPT9 (urban) are mostly higher than those at KMIT station (suburban). In addition, we investigate the effects of high (severe) RFI events on single-point and real-time kinematics (RTK) positioning errors.
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    Statistical analysis and effects of radio frequency interference in GPS signal quality in Thailand
    (2024-10-01)
    Sophan, Somkit
    ;
    Supnithi, Pornchai
    ;
    Myint, Lin M.M.
    ;
    Budtho, Jirapoom
    ;
    Saito, Susumu
    The radio frequency interference (RFI) in global navigation satellite system (GNSS) signals has recently received much attention in the GNSS community because of frequent jamming issues. The carrier-to-noise density ratio (C/N<inf>0</inf>) is one of the common parameters to indicate the signal quality. In this work, we propose a real-time RFI analysis based on windowing and normalization of C/N<inf>0</inf> observations. Specifically, the percentage of RFI values are analyzed based on the modified RFI detection. The steps to analyze the RFI levels (low, medium, high) are highlighted. In addition, we analyzed the occurrences of local RFI effects in areas surrounding the Suvarnabhumi International Airport as well as remote areas. We validate the modified RFI detection by using the GNSS reference stations at the urban, suburban, and outside the capital city in Thailand. The user positioning errors with the high (severe) RFI levels are investigated based on the single point positioning (SPP) and real-time kinematics (RTK). From the experimental simulations, the high RFI levels at the urban are higher than those at the suburban. As expected, the statistical analysis covering COVID-19 (2019 to 2023) shows that the high RFI levels in June 2023 (post COVID-19) are more than those in June 2020 and 2021 (lockdown COVID-19) by about twofold. Additionally, the SPP positioning errors with the medium/high RFI levels are clearly seen. There are more floating solutions in the RTK system in the year with more RFI presence.
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    Ground Facility Error Analysis and GBAS Performance Evaluation Around Suvarnabhumi Airport, Thailand
    (2024-02-01)
    Budtho, Jirapoom
    ;
    Supnithi, Pornchai
    ;
    Siansawasdi, Nattapong
    ;
    Saito, Susumu
    ;
    Saekow, Apitep
    The performances of the ground-based augmentation system (GBAS) designed for the landing phase of aircraft rely on the accurate characterization of error models. Among various error sources, the multipath model, which is typically constructed by combining environmental errors at airports, must be modeled in GBAS. However, in practice, the multipath effects at a particular airport differ from other airports due to distinct construction sites and continually changing environments, resulting in an inaccurate error model in GBAS operations. Therefore, in this article, we develop and evaluate a 2-D ground facility error model from the Global Navigation Satellite System Stations (GNSS) at the Suvarnabhumi International Airport in Bangkok, Thailand. The results indicate that the elevation and azimuth grid points require around seven days of observation data to create the GBAS ground facility error model for GBAS operation. The number of observations per day at each elevation and azimuth grid point will determine the data requirements for the complete building of the 2-D ground error model. When the proposed model is applied to the GBAS simulation, it is found that the proposed 2-D ground error model reduces the root-mean-square deviation (RMSD) of positioning errors by around 0.4% to 3.5% when compared to the 1-D error model and the category B Ground accuracy designator model, respectively. The maximum vertical protection level reduction of the proposed 2-D B-value model in comparison with the reference 1-D B-value is 0.24 m, about a 6% reduction.
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