A Satellite Based Augmentation System (SBAS) is a system that provides positioning information with high and accurate reliability to users who require ensuring high safety such as airplane taking off and landing. A continuous performance evaluation on navigation safety facilities shall be performed ...
A Satellite Based Augmentation System (SBAS) is a system that provides positioning information with high and accurate reliability to users who require ensuring high safety such as airplane taking off and landing. A continuous performance evaluation on navigation safety facilities shall be performed to determine whether developed systems meet the required performance before and after the operation. In this paper, SBAS position domain analysis is discussed in relation to analysis items for performance evaluation. The performance evaluation on the SBAS in the position domain shall conduct analysis on accuracy, integrity, continuity, and availability, which are items in the required navigation performance (RNP). In the paper, position domain analysis was conducted with regard to the Wide Area Augmentation System (WAAS) in the USA and the European Geostationary Navigation Overlay Service (EGNOS), which were developed already and now under operation. The analysis result showed that each of the systems satisfied the APV-I performance requirements recommended by the International Civil Aviation Organization (ICAO) with regard to daily data. It is necessary to verify using long-term data, whether the performance requirements in the RNP items are satisfied for system certification.
A Satellite Based Augmentation System (SBAS) is a system that provides positioning information with high and accurate reliability to users who require ensuring high safety such as airplane taking off and landing. A continuous performance evaluation on navigation safety facilities shall be performed to determine whether developed systems meet the required performance before and after the operation. In this paper, SBAS position domain analysis is discussed in relation to analysis items for performance evaluation. The performance evaluation on the SBAS in the position domain shall conduct analysis on accuracy, integrity, continuity, and availability, which are items in the required navigation performance (RNP). In the paper, position domain analysis was conducted with regard to the Wide Area Augmentation System (WAAS) in the USA and the European Geostationary Navigation Overlay Service (EGNOS), which were developed already and now under operation. The analysis result showed that each of the systems satisfied the APV-I performance requirements recommended by the International Civil Aviation Organization (ICAO) with regard to daily data. It is necessary to verify using long-term data, whether the performance requirements in the RNP items are satisfied for system certification.
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제안 방법
In this study, PE and PL were calculated by projecting pseudorange residual and standard deviation calculated in the range domain analysis module into the position domain. Furthermore, performances of accuracy, integrity, and availability of SBAS users were evaluated and then, whether the performances satisfy the ICAO performance requirements was analyzed. The EGNOS provides APV-I service, and the WAAS provides LPV-200 service, which is similar to APV-I but the vertical performance requirement was strengthened in.
In order to verify whether an SBAS system satisfies the navigation performance requirements specified by the ICAO, analysis on accuracy, integrity, continuity, and availability defined as items in the RNP should be performed. We investigated the definition and analysis method about the four RNP items and outcome results through periodical performance analysis report provided by the WAAS and the EGNOS as well as ICAO SARPs (ICAO 2006), WAAS Performance Standard (FAA 2008), and EGNOS Safety of Life Document (ESSP 2014), which are official documents in relation to SBAS performance analysis (Han et al.
1 shows a schematic diagram of the SBAS position domain analysis module developed by our research team. In this study, PE and PL were calculated by projecting pseudorange residual and standard deviation calculated in the range domain analysis module into the position domain. Furthermore, performances of accuracy, integrity, and availability of SBAS users were evaluated and then, whether the performances satisfy the ICAO performance requirements was analyzed.
Since this study did not aim to calculate an accurate position error, pseudorange residual errors were not calculated from measurement data in a real receiver but residual errors of satellite, the ionosphere, and tropospheric delay errors that were corrected from real SBAS messages were calculated directly to acquire a pseudorange residual error.
For satellite-related residual errors, a satellite position calculated by broadcasting ephemeris was corrected into SBAS satellite correction and then the error was calculated based on a difference compared to that of the precise orbit coordinate. The ionospheric delay residual error was calculated by correcting slant ionospheric delay generated from the IONEX precise ionosphere data using SBAS ionosphere correction and then a residual error was calculated. The tropospheric delay residual error was corrected by correcting slant tropospheric delay generated from the Saastamoinen model using SBAS tropospheric model and then a residual error was calculated.
The purpose of the study is focused on presenting performance analysis method of each RNP item and case study on outputs rather than providing accurate performance analysis results in position domain. Thus, performance analysis results in the position domain were derived through daily data processing and whether the performance requirements were met or not was verified.
Thus, performance analysis results in the position domain were derived through daily data processing and whether the performance requirements were met or not was verified. The results in this study do not represent a level of performance in real systems so it is necessary to perform the method proposed in this paper for a long-term basis to conduct system certification.
The ionospheric delay residual error was calculated by correcting slant ionospheric delay generated from the IONEX precise ionosphere data using SBAS ionosphere correction and then a residual error was calculated. The tropospheric delay residual error was corrected by correcting slant tropospheric delay generated from the Saastamoinen model using SBAS tropospheric model and then a residual error was calculated.
대상 데이터
For data used to analyze the performance of SBAS position domain, currently available data used in the WAAS in the USA and the EGNOS data in Europe were selected. The WAAS and EGNOS provide SBAS correction messages by the RINEX format through FTP servers.
성능/효과
Table 3 presents the accuracy performance analysis results in the WAAS and EGNOS. A 95% cumulative error of WAAS users was calculated as horizontal 0.49 m and vertical 0.78 m while a 95% cumulative error of EGNOS users was calculated as horizontal 0.60 m and vertical 1.34 m, indicating both of them satisfied APV-I accuracy-related requirements in the corresponding analysis date.
In the position service accuracy analysis, thus, statistics of user's positioning error, in which correction information of SBAS is applied, is calculated, and whether daily horizontal and vertical 95% accuracy exceeds a value specified in the RNP performance requirement is verified.
We also conducted performance analysis on users of the WAAS in the USA and EGNOS in Europe through the SBAS position domain analysis tool developed by our research team. The analysis result showed that both of currently running WAAS and EGNOS satisfied APV-I accuracy, integrity, and availability performance requirements suggested by the ICAO.
Web sites of the WAAS NSTB in the Federal Aviation Administration (FAA) in the USA and EGNOS User Support in the European Satellite Services Provider (ESSP) in Europe analyze daily service coverage map and provide the analysis results continuously. We verified whether correct coverage was calculated by comparing the coverage (refer to Figs. 13 and 14), provided by each institution at the corresponding date and availability coverage analyzed by the tool developed in the present study, and found that 99% coverage boundary was consistent.
참고문헌 (9)
ESSP 2014, EGNOS Safety of Life (SoL) Service Definition Document, vol. 2.1
Han, D. H., Kim, J. B., Kim, D. U., Park, B. W., Lee, J. Y., et al. 2016, Analysis on elementary technology of operational test for KASS performance evaluation, in 2016 SASE Spring Conference, Jeju: Korea, pp.79-80
ICAO 2006, International Standards and Recommended Practices (SARPs): Aeronautical Telecommunications, Annex 10, vol.1, 6th edition
Nam, G.-W. 2015, South Korea launches Korean SBAS, CNS TODAY, 4, 4-9
RTCA 2006, Minimum Operational Performance Standards for Global Positioning System/Wide Area Augmentation System Airborne Equipment, DO-229D
Sin, C. S., Kim, J. H., & Ahn, J. Y. 2014, Technical development trends of satellite based augmentation system, Electronics and Telecommunications Trends, 29, 74-85
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