Budtho, Jirapoom

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Budtho, Jirapoom
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Budtho, J.
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jirapoom.bu@kmitl.ac.th

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    Item type:Publication,
    Nominal ionospheric delay gradient estimation at Suvarnabhumi airport, Thailand
    (2017-10-19)
    Budtho, Jirapoom
    ;
    Supnithi, Pornchai
    ;
    Saekow, Apitep
    ;
    Saito, Susumu
    Ground-Based Augmentation System (GBAS) allows high-precision aircraft landing based on Global Navigation Satellite System (GNSS) at large airports. However, non-uniform spatial ionospheric delay needs to be determined. In this work, we compute the nominal ionospheric delay gradients around Suvarnabhumi airport, Thailand. The utilized techniques involve Kalman filter and LAMBDA method. Based on the measurements on DOY 043 of 2015, we found that the ionospheric delay gradients are less than 20 mm/km. With the improved ambiguity ratio test to obtain higher success rate than previous works, the standard deviation σ<inf>VIC</inf> is 5.27 mm/km.
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    Analysis of Quiet Time Vertical Ionospheric Delay Gradients Around Suvarnabhumi Airport, Thailand
    (2018-09-01)
    Budtho, J.
    ;
    Supnithi, P.
    ;
    Saito, S.
    Global Navigation Satellite System (GNSS) is vital to aircraft navigation at many phases of flight. To extend its use to the approach and landing phases, ground-based augmentation system is an important on-the-ground technology to reduce the positioning errors. However, nonuniform spatial ionospheric delays need to be assessed during ground-based augmentation system planning at each airport, particularly, in equatorial and low-latitude regions. In this work, we analyze the statistics of ionospheric delay gradients around Suvarnabhumi airport, Thailand. The ionospheric delay gradients are estimated using single-frequency code and carrier phase observation through the Kalman filter. To increase the success of the ratio test, the satellite elimination technique is then proposed. Based on the analysis between 2013 and 2016, we find that the background ionospheric delay gradients during equinox are higher than solstice, especially during September equinox 2013 when the gradients are about 9 mm/km. Moreover, the ionospheric delay gradients are more variable during daytime than nighttime.
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    The Improvement of Time-step method for Ionospheric Delay gradient Estimation
    (2019-06-01)
    Budtho, Jirapoom
    ;
    Supnithi, Pornchai
    ;
    Saito, Susumu
    Ground-Based Augmentation System (GBAS) is concerned with the aircraft positioning correction for precision landing. The ionospheric irregularity is a major impediment of the performance of GBAS. When an airport has at least 2 Global Navigation Satellite System (GNSS) stations, the ionospheric delay gradients can be obtained by using the dual-frequency GNSS stations. If there is only 1 GNSS station in the area, the time step-method can be used. Normally, the baseline from the time-step method is varied according to the sampling rate of GNSS data. Although the sampling rate of the GNSS receiver is a constant value, the baseline varies due to the speed of the GNSS satellite, observed from the ground reference, which can be up to 20 difference km. This paper proposes the dynamic Time-Step method which designates the baseline by adjusting the time between 2 snapshots. The results show that the range of baseline from the reference time-step method, which is set to 1 minute of the sampling rate, can be reduced to 0.5-km variation.