# Construction Progress and Aviation Flight Test of BDSBAS
###### Abstract  
As an important part of the BeiDou global navigation satellite system (BDS-3), the BeiDou satellite-based augmentation system (BDSBAS) aims to provide a high-integrity navigation service for users in China and its surrounding areas. At present, BDSBAS has completed the preliminary construction of the system and formed the single frequency (SF) augmentation service. The paper introduces the composition and working process of BDSBAS, and expounds the solution and performance evaluation methods of the BDSBAS SF service. Tests based on a general aviation aircraft were carried out at Caihu Airport in Shenyang, China, which simulated the aircraft's take-off and landing operation during the approach phase and the transition flight operation during the en-route phase. On this basis, the BDSBAS SF service performance was analyzed and evaluated. The horizontal positioning errors of the three flight tests are 1.62, 1.27, and 1.49 m, respectively, and the vertical positioning errors are 4.38, 4.30, and 4.04 m, respectively. In the first two tests, the APV-I availability and continuity of the service reach 100%. In the last test, a receiver false alarm event occurred, resulting in an APV-I availability and continuity of 99.993% and 99.989%, respectively. The event was confirmed to be caused by some aviation environmental factors and was not related to the system service. No integrity events occurred during the tests. The test results show that the positioning accuracy, availability, and integrity of the BDSBAS SF service meet the APV-I level requirements of the ICAO standards, which preliminarily illustrates the ability of BDSBAS to be used in the field of civil aviation. GNSS; BeiDou; BDS-3; BDSBAS; SBAS; APV-I; CAT-I 2022 28 February 2022 28 February 2022 22 March 2022 28 February 2022 28 March 2022 28 February 2022 28 February 2022 28 March 2022 28 February 2022 28 March 2022 28 February 2022 28 February 2022 28 March 2022 28 February 2022 28 March 2022 28 February 2022 28 March 2022 28 February 2022 28 February 2022 2  
125,000 aircraft have been equipped with WAAS receivers [7]. In the summer of 1994, Stanford performed WAAS flight trials to provide WAAS operational experience [8]. The flight trials used three WAAS reference stations (WRSs), which Stanford installed for the FAA in the western United States, and also used Professor [PERSON]'s Piper Dakota to fly WAAS precision approaches to an un-instrumented airport (Palo Alto). The WAAS corrected pseudo-ranges are used to calculate the aircraft location and glide path deviations. This entire process occurs in real time and yields vertical errors better than 3 m 95 percent of the time. EGNOS provides three types of services: open service (OS) since October 2009 [9], safety of life (SoL) service, since March 2011 [10], and EGNOS data access service (EDAS) service, since July 2012 [11]. The availability of EGNOS's NPA operation in all European Civil Aviation Conference (ECAC) regions exceeds 0.999, and the APV-I and LPV200 operations in most of ECAC landmasses exceed 0.99 [12]. In May 2016, EGNOS completed the first LPV200 approach at the Paris-Charles de Gaulle airport. As of today, EGNOS has more than 331 LPV programs, and more than 167 LPV200 programs, serving more than 167 airports [12]. In recent years, EGNOS has continued to promote the expansion of coverage and service scope, for example, in countries or regions such as South Africa, Ukraine, the Middle East, and the Mediterranean [13]. Aviation flights test were conducted in [14] by using a Cessna 172 aircraft equipped with an EGNOS airborne receiver. Among them, the positioning error of the test at the EPDE military aerodrome in Deblin is less than 2.1m, and the integrity of positioning does not exceed 19m; the positioning error of the test at the Deputycze Krolewskie aerodrome EPCD is less than 2.1 m, and the integrity of positioning does not exceed 19 m. Moreover, the availability parameter was found to be 100%.