A Satellite Based Augmentation System (SBAS) provides differential correction and integrity information through geostationary satellite to users in order to reduce Global Navigation Satellite System (GNSS)-related errors such as ionospheric delay and tropospheric delay, and satellite orbit and clock...
A Satellite Based Augmentation System (SBAS) provides differential correction and integrity information through geostationary satellite to users in order to reduce Global Navigation Satellite System (GNSS)-related errors such as ionospheric delay and tropospheric delay, and satellite orbit and clock errors and calculate a protection level of the calculated location. A SBAS is a system, which has been set as an international standard by the International Civilian Aviation Organization (ICAO) to be utilized for safe operation of aircrafts. Currently, the Wide Area Augmentation System (WAAS) in the USA, the European Geostationary Navigation Overlay Service (EGNOS) in Europe, MTSAT Satellite Augmentation System (MSAS) in Japan, and GPS-Aided Geo Augmented Navigation (GAGAN) are operated. The System for Differential Correction and Monitoring (SDCM) in Russia is now under construction and testing. All SBASs that are currently under operation including the WAAS in the USA provide correction and integrity information about the Global Positioning System (GPS) whereas the SDCM in Russia that started SBAS-related test services in Russia in recent years provides correction and integrity information about not only the GPS but also the GLONASS. Currently, LUCH-5A(PRN 140), LUCH-5B(PRN 125), and LUCH-5V(PRN 141) are assigned and used as geostationary satellites for the SDCM. Among them, PRN 140 satellite is now broadcasting SBAS test messages for SDCM test services. In particular, since messages broadcast by PRN 140 satellite are received in Korea as well, performance analysis on GPS/GLONASS Multi-Constellation SBAS using the SDCM can be possible. The present paper generated correction and integrity information about GPS and GLONASS using SDCM messages broadcast by the PRN 140 satellite, and performed analysis on GPS/GLONASS Multi-Constellation SBAS performance and APV-I availability by applying GPS and GLONASS observation data received from multiple reference stations, which were operated in the National Geographic Information Institute (NGII) for performance analysis on GPS/GLONASS Multi-Constellation SBAS according to user locations inside South Korea utilizing the above-calculated information.
A Satellite Based Augmentation System (SBAS) provides differential correction and integrity information through geostationary satellite to users in order to reduce Global Navigation Satellite System (GNSS)-related errors such as ionospheric delay and tropospheric delay, and satellite orbit and clock errors and calculate a protection level of the calculated location. A SBAS is a system, which has been set as an international standard by the International Civilian Aviation Organization (ICAO) to be utilized for safe operation of aircrafts. Currently, the Wide Area Augmentation System (WAAS) in the USA, the European Geostationary Navigation Overlay Service (EGNOS) in Europe, MTSAT Satellite Augmentation System (MSAS) in Japan, and GPS-Aided Geo Augmented Navigation (GAGAN) are operated. The System for Differential Correction and Monitoring (SDCM) in Russia is now under construction and testing. All SBASs that are currently under operation including the WAAS in the USA provide correction and integrity information about the Global Positioning System (GPS) whereas the SDCM in Russia that started SBAS-related test services in Russia in recent years provides correction and integrity information about not only the GPS but also the GLONASS. Currently, LUCH-5A(PRN 140), LUCH-5B(PRN 125), and LUCH-5V(PRN 141) are assigned and used as geostationary satellites for the SDCM. Among them, PRN 140 satellite is now broadcasting SBAS test messages for SDCM test services. In particular, since messages broadcast by PRN 140 satellite are received in Korea as well, performance analysis on GPS/GLONASS Multi-Constellation SBAS using the SDCM can be possible. The present paper generated correction and integrity information about GPS and GLONASS using SDCM messages broadcast by the PRN 140 satellite, and performed analysis on GPS/GLONASS Multi-Constellation SBAS performance and APV-I availability by applying GPS and GLONASS observation data received from multiple reference stations, which were operated in the National Geographic Information Institute (NGII) for performance analysis on GPS/GLONASS Multi-Constellation SBAS according to user locations inside South Korea utilizing the above-calculated information.
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제안 방법
A process of the user positioning calculation is as follows: First, GLONASS L1 code measurement, satellite signal reception times, and GLONASS broadcast ephemeris are received as input data and GLONASS satellite position and clock errors are calculated as of the time of the satellite signal transmission.
In order to determine the reason for performance degradation in Multi-Constellation SBAS in the SDCM as a latitude moved from higher to lower latitude, fast correction, long-term correction, and ionospheric correction were analyzed. The analysis result showed that the mean numbers of visible satellites were approximately 17 satellites in higher latitude and 16 satellites in lower latitude, which showed no significant difference.
In order to determine the reason for significant performance degradation of GPS/GLONASS Multi-Constellation SBAS as a latitude moved from higher to lower latitude in South Korea, performance was analyzed in terms of fast correction, long-term correction, and ionospheric correction.
In this paper, we generated differential correction and integrity information with regard to GPS and GLONASS by receiving PRN 140 messages from the SDCM satellite of Russia, which has started a test service of SBAS in Russia, and analyzed performance in Multi-Constellation SBAS in the Korean Peninsula utilizing the above information. To do this, 17 reference stations running by the National Geographic Information Institute were selected, and characteristics of messages and accuracy and integrity characteristics received from 2016/9/24 00:00 and 2016/9/24 24:00 were verified thereby performing performance analysis.
In particular, since the Korean Peninsula is covered by the service area of the PRN 140 satellite and messages broadcast by PRN 140 satellite are received in Korea as well, performance analysis on GPS/GLONASS Multi-Constellation SBAS using the SDCM can be possible. Thus, the present paper generated correction and integrity information about GPS and GLONASS using SDCM messages broadcast by the PRN 140 satellite, and performed analysis on GPS/GLONASS Multi-Constellation SBAS performance and APV-I availability by applying GPS and GLONASS observation data received from multiple reference stations, which were operated in the National Geographic Information Institute (NGII).
대상 데이터
In order to consider various user positions from low to high latitudes in South Korea, the following 17 GNSS reference stations that are operated by the National Geographic Information Institute are selected as shown in Fig. 4: Cheorwon Reference Station (CHUL), Inje Reference Station (INJE), Ganghwa Reference Station (GANH), Hongcheon Reference Station (HONC), Seoul Reference Station (SOUL), Donghae Reference Station (DONH), Incheon Reference Station (INCH), Suwon Reference Station (SUWN), Boeun Reference Station (BOEN), Gunsan Reference Station (KUSN), Muju Reference Station (MUJU), Ulsan Reference Station (WOLS), Busan Reference Station (PUSN), Suncheon Reference Station (SONC), Geoje Reference Station (GOJE), Jangheung Reference Station (JAHG), Jeju Reference Station (CHJU).
성능/효과
Table 7 summarizes detailed results for each reference station. As the same as the analysis result on position errors, horizontal and vertical PLs were increased as a latitude moved from higher to lower latitude in South Korea, and APV-I availability was decreased accordingly. In particular, mean values of horizontal and vertical PLs at CHJU Reference Station were 42.
5 and Table 5, RMSs of horizontal and vertical errors were increased as a latitude is moved from higher latitude to lower latitude in South Korea. In particular, RMSs of horizontal and vertical errors in CHUL Reference Station, which was located in the northernmost part among the selected reference stations, were 0.8857 m and 1.0276 m, respectively, while those in CHJU Reference Station, which was located in the southernmost part, were 1.9322 m and 2.1862 m, verifying that a user positioning error of the GPS/GLONASS Multi-Constellation SBAS was twice that in the high latitude approximately, resulting in a significant decrease in performance.
As the same as the analysis result on position errors, horizontal and vertical PLs were increased as a latitude moved from higher to lower latitude in South Korea, and APV-I availability was decreased accordingly. In particular, mean values of horizontal and vertical PLs at CHJU Reference Station were 42.5063 m and 59.0544 m, respectively, which were 2.5 to 2.7 times higher than 15.6189 m and 22.9821 m, which were values at CHUL Reference Station, verifying that the PL was rapidly increased as a latitude moved from higher to lower latitude. Furthermore, APV-I availabilities at CHUL and DONH Reference Stations in the horizontal and vertical directions showed 99.
It is also expressed conventionally as a ratio of time that the protection level (PL) is less than the alert limit (AL). In this paper, we investigated a possibility whether performance of APV-I level is satisfied from viewpoints of AL and horizontal and vertical PL calculated using data collected in 24 hours assuming that accuracy, integrity, and continuity in the SDCM system in South Korea satisfy the performance requirements of APV-I level.
The analysis result on correction performance of user positioning showed that horizontal and vertical errors tended to increase as users in South Korea were located in lower latitude. For example, errors calculated in the southernmost reference station amounted to twice of that in the northernmost reference station approximately.
In order to determine the reason for performance degradation in Multi-Constellation SBAS in the SDCM as a latitude moved from higher to lower latitude, fast correction, long-term correction, and ionospheric correction were analyzed. The analysis result showed that the mean numbers of visible satellites were approximately 17 satellites in higher latitude and 16 satellites in lower latitude, which showed no significant difference. However, the mean numbers of satellites used in user positioning calculation were approximately 13 satellites in higher latitude and 9 satellites in lower latitude, which verified the decrease in the number of satellites used in user positioning calculation in lower latitude.
The analysis result showed that the number of satellites that can generate ionospheric correction was 17 satellites in CHUL reference station and 6 satellites in CHJU reference station due to the characteristics of the SDCM that did not provide ionospheric correction information with regard to IGP below 35° latitude over the Korean Peninsula.
Second, GLONASS L1 code measurement, satellite signal receive time, and GLONASS broadcast ephemeris are received as input data and user position and clock errors are calculated in the stand-alone mode. Third, decoded SDCM message, GLONASS satellite position, and clock errors are received as input data and fast correction and long-term correction, which are GLONASS satellite-related correction information, and ionospheric correction and tropospheric correction, which are atmosphere-related errors, are calculated. Finally, SDCM correction is applied to GLONASS L1 code measurements to calculate user position and clock errors at the SBAS mode.
후속연구
As such, a difference in the number of satellites that can generate ionospheric correction was verified as the main reason for the regional difference in performance of GPS/GLONASS Multi-Constellation SBAS using the SDCM. For future study, it is necessary to investigate possibility of improvements on performance degradation through interlink with other systems.
참고문헌 (12)
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