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Ground Facility Error Analysis and GBAS Performance Evaluation Around Suvarnabhumi Airport, Thailand
(2024-02-01)
Budtho, Jirapoom
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Supnithi, Pornchai
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Siansawasdi, Nattapong
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Saito, Susumu
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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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Study on Effect of Equatorial Plasma Bubble over Real-Time Kinematic Positioning in Bangkok Thailand
(2022-01-01)
Thu, Phyo C.
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Supnithi, Pornchai
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Myint, Lin Min Min
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Budtho, Jirapoom
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Saito, Susumu
Equatorial plasma bubbles (EPBs) depict local ionospheric irregularity in low-latitude regions which can spread to mid-latitude regions. In this work, we analyzed the effects of the EPBs on the performance of real-time kinematic (RTK) positioning at the short, medium, and long baselines in Bangkok, Thailand. We used the kinematic positioning mode provided by a free and open-source software (FOSS) package called RTKLIB to analyze the positioning errors. It is found that the positioning errors are higher during the disturbance periods and more severe in the long baseline case.
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Multipath Analysis at Low-Latitude GNSS Stations around Suvarnabhumi Airport, Thailand, for GBAS Standards
(2021-01-01)
Budtho, Jirapoom
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Supnithi, Pornchai
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Saito, Susumu
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Siansawasdi, Nattapong
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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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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
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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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Ionospheric delay gradient monitoring for GBAS by GPS stations near Suvarnabhumi airport, Thailand
(2015-10-01)
Rungraengwajiake, Sarawoot
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Supnithi, Pornchai
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Saito, Susumu
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Siansawasdi, Nattapong
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Saekow, Apitep
Ground-based augmentation system (GBAS) is an important augmentation system that provides the differential corrections and integrity information from the reference stations to the aircrafts for precision approach and landing. It is known that the nonuniform ionospheric characteristics called "ionospheric delay gradient" can cause the errors in differential corrections degrading the accuracy and safety level if they are undetected by the reference stations. Since the characteristics of the ionosphere are different for each region, the ionospheric delay gradient observations in equatorial and low-latitude regions are necessary for developing the suitable ionospheric threat models. The purpose of this work is to analyze the ionospheric delay gradients observed by three GPS stations near Suvarnabhumi airport in Bangkok, Thailand, which is located in the low-latitude region. The ionospheric irregularities in this region are mainly caused by the plasma bubble, which usually occurs after sunset. The GPS data with plasma bubble occurrence during the September equinox 2011 and 2012 are therefore analyzed. In addition, the data analysis procedure utilizing the rate of total electron content change index for this region is proposed. The results show that the ionospheric delay gradients observed in the west-east direction appear higher than the south-north direction, varying from 28 to 178 mm/km during plasma bubble occurrences.
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Drift velocity estimation of ionospheric disturbance using GPS observations
(2014-01-01)
Bumrungkit, Acharaporn
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Rungraengwajiake, Sarawoot
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Supnithi, Pornchai
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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
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Supnithi, Pornchai
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Saito, Susumu
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Siansawasdi, Nattapong
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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
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Supnithi, Pornchai
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Kenpankho, Prasert
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Saekow, Apitep
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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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