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    Multipath Analysis at Low-Latitude GNSS Stations around Suvarnabhumi Airport, Thailand, for GBAS Standards
    (2021-01-01)
    Budtho, Jirapoom
    ;
    Supnithi, Pornchai
    ;
    Saito, Susumu
    ;
    Siansawasdi, Nattapong
    ;
    Saekow, Apitep
    The characteristics of the local area positioning error sources are important for Ground-Based Augmentation System (GBAS) service planning. Accurate standard deviation models are required for prior simulation of the performance of the aircraft precision landing system. The multipath standard deviation of the pseudo-range errors model is used in GBAS for each satellite elevation angle. This standard model is generated by collecting the multipath conditions from airports. However, some airports have different characteristics of the multipath effects than the others, resulting in inaccurate error models when applied to the GBAS operations. Therefore, in this work, we study and analyze a 1-dimensional curve-fitted model for the multipath error models at three GNSS stations near the Suvarnabhumi International Airport, Thailand. The results show that in the case that the multipath errors are distributed equally at each azimuth angle, the RMSEs are reduced from 0.1 to 0.02 meters near the 90-degree elevation angle and less than 0.05 meters at other degrees. For the AER1 station, located on the airport runway, in which the multipath errors are not distributed equally at each azimuth, the maximum RMSE, is less than 0.08 meters when compared with 0.14 meters from the GBAS model.
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    Preliminary results of EPB impact on GBAS performance
    (2019-06-01)
    Bumrungkit, Acharaporn
    ;
    Phakphisut, Watid
    ;
    Supnithi, Pornchai
    In the low-latitude region, equatorial plasma bubbles (EPBs) frequently occur. Ionospheric irregularity due to EPBs can degrade the performance of ground-based augmentation system (GBAS) in aviation. This work focuses on the impact of multiple EPBs on GBAS performance. The multiple EPBs with varied separation distances are simulated to assess the performance of GBAS in Thailand. From the simulation, the results show that the 100 km separation distance causes a more hazardous error in vertical than 1200 km separation distance between the EPBs.
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    The GBAS protection levels and availability during ionospheric irregularity occurrence
    (2016-09-06)
    Limjumroonrat, Chayanan
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    Rungraengwajiake, Sarawoot
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    Supnihi, Pornchai
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    Supanunt, Wisanu
    ;
    Siansawasdi, Nattapong
    The next generation aeronautical navigation system utilizes the Global navigation satellite system (GNSS) based equipment to aid aircrafts during approaching and landing. The Ground-based augmentation system (GBAS) broadcasts the augmentation information to the aircrafts in order to compensate for the GNSS signal-in-space errors and provides the accuracy, integrity, continuity and availability of system. The protection level is a parameter in the Standards and Recommended Practices (SARPs) from the International Civil Aviation Organization (ICAO) GBAS standard which validates the availability of system. The ICAO SARPs's algorithms are applied in this paper to compute the GBAS protection levels. We use the GNSS data recorded at the Suvarnnahumi international airport (AERO) in 2014. The results show statistics of days with ionospheric irregularity in 2014 as well as the protection levels during ionospheric irregularity occurrences. The average of the availability in March (equinox) is 99.30% and July (solstice) is 99.93% at the altitude of 100 feet. But the average availability of September (equinox) is 99.98%. So, that will be another reason that reduce the availability unless the ionospheric irregularity.
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    Drift velocity estimation of ionospheric disturbance using GPS observations
    (2014-01-01)
    Bumrungkit, Acharaporn
    ;
    Rungraengwajiake, Sarawoot
    ;
    Supnithi, Pornchai
    ;
    Siansawasdi, Nattapong
    The Ground-Based Augmentation System (GBAS) based on the global positioning system (GPS) is used for positioning accuracy improvement of the aircraft landing. However, the ionospheric irregularity can cause irregular electron density that affects the accuracy of GBAS system. In this work, we analyze the drift velocity of ionospheric irregularity or plasma bubble phenomenon by using the correlation time of slant total electron content (STEC) from two GPS receivers that are located near Suvarnabhumi airport, Thailand. The data on September 1<sup>st</sup>, 2011 with the plasma bubble occurrence is analyzed. The result shows the drift velocity of plasma bubbles is about 108 meterspersecond (m/s). © 2014 IEEE.
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    Study of ionospheric delay gradient based on GPS monitoring stations near Suvarnabhumi airport in Thailand
    (2014-01-01)
    Rungraengwajiake, Sarawoot
    ;
    Supnithi, Pornchai
    ;
    Saito, Susumu
    ;
    Siansawasdi, Nattapong
    ;
    Saekow, Apitep
    The ionospheric delay gradient is an important parameter for the planning of ground-based augmentation system (GBAS) in a region. When it is beyond the limit, the integrity and safety for landing approach of CAT II/III may be compromised. In order to maintain the availability and safety requirement of the system, the ionospheric threat models have been developed in several countries during the past few years. However, the ionospheric delay gradient associated with plasma bubble in low latitude region has not been studied well. In this work, we present some analytical results of ionospheric delay gradient based on three GPS monitoring stations near Suvarnabhumi airport in Thailand. The stations are located on the campus of King Mongkut's Institute of Technology Ladkrabang (13.7278°N, 100.7726°E), Stamford University (13.7356°N, 100.6612°E) and Suvarnabhumi airport (13.6945°N, 100.7608°E). The analyzed results on 1st September 2011 show that the ionospheric delay gradient varies from -95.23 to 107.7 mm/km during the occurrence of the plasma bubbles. © 2014 Springer.
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    Preliminary results of ionospheric delay gradients study near Suvarnabhumi airport in Thailand
    (2013-12-09)
    Runraengwajiake, Sarawoot
    ;
    Supnithi, Pornchai
    ;
    Kenpankho, Prasert
    ;
    Saekow, Apitep
    ;
    Saito, Susumu
    Ground-Based Augmentation System (GBAS) is an augmentation system support for GNSS to provide a differential correction and integrity information to the aircraft for landing approach. However, the ionospheric disturbances can cause the ionospheric delay gradient between the reference stations and the aircraft and may degrade the accuracy and safety level of GBAS. In this work, we present some preliminary results of the ionospheric delay gradients in terms of the difference of slant TEC (total electron content) using GPS monitoring stations near Suvarnabhumi International airport, Bangkok, Thailand. Based on the data on 1<sup>st</sup> September, 2011, the results show that the slant TEC between two nearby stations are different during plasma bubble occurrence. In addition, we also compute the speed of moving plasma bubble by estimating the delay time between slant TEC patterns. © 2013 IEEE.
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    Measurement and simulation of equatorial ionospheric plasma bubbles to assess their impact on GNSS performance
    (2012-01-01)
    Tsujii, Toshiaki
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    Fujiwara, Takeshi
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    Kubota, Tetsunari
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    Satirapod, Chalermchon
    ;
    Supnithi, Pornchai
    Ionospheric anomaly is one of the major error sources which deteriorate the GNSS performance. In the equatorial region, effects of the ionospheric plasma bubbles are of great interest because they are pretty common phenomena, especially in the period of the high solar activity. In order to evaluate the GNSS performance under circumstance of the bubbles, an ionospheric scintillation monitor has been developed and installed in Bangkok, Thailand. Furthermore, a model simulating the ionospheric delay and scintillation due to the bubbles has been developed. Based on these developments, the effects of the simulated plasma bubbles are analyzed and their agreement with the real observation is demonstrated. An availability degradation of the GPS ground based augmentation system (GBAS) caused by the bubbles is exampled in details. Finally, an integrated GPS/INS approach based on the Doppler frequency is proposed to remedy the deterioration.