Enhanced Sbas With Satellite Dynamic Mask And Precise Orbit And Clock Corrections

Development and deployment of SBAS systems are a technological challenge, as it is the definition of the evolution of the SBAS standard. Presently, WAAS in US. MSAS in Japan. and EGNOS in Europe have been declared operational and available for civil aviation. Other SBAS systems are in development or validation phases, such as the Indian GAGAN or the Russian SDCM. Although most of these systems aim at the exclusive augmentation of the GPS constellation in the short term. SDCM already pursues the service for GLONASS and GPS, and other service providers are working in the evolution towards multi-constellation as part of the additional services to be enabled with the new SBAS LI/L5 standard, which is being defined at present. The potential new services arc not Just restricted to the signals or the core GNSS constellations to be augmented; the target civil aviation services could go beyond LPV-200 procedures to new supported operations, such as Autoland.As a consequence of the technological challenge, it is usual that SBAS development plans envisage the deployment of SBAS test beds (e.g.: WAAS NSTB, EGNOS ESTB) and pre-operational, non-certified, services prior to the operational system development first stages. Test beds offer numerous advantages, in particular provide the system developers or standard designers with powerful platforms to early validate new concept architectures, first design solutions and performance assumptions. thus greatly mitigating design risks and helping to optimize the design to satisfy the requirements of the system. magicSBAS is a state-of-the-art real time operational SBAS testbed developed by GMV to offer non-safety critical SBAS augmentation to any interested region or organization. The algorithms implemented in magicSBAS have been fully developed by GMV and are the result of more than 15 years of experience in the development of EGNOS and other SBAS programs. The magicSBAS algorithms, originally designed to mimic EGNOS performances over the ECAC service area, have been further optimized and tuned to provide the best performances in other regions of the world (South America, South Africa, Russian Federation, etc.).Recentl), magicSBAS has evolved to cover key functionalities for multi-constellation augmentation and for more stringent target flight phases. The new functions added are the following:- A: Satellite PRN dynamic mask management: PRN dynamic mask is allowed in the current SBAS LI standard and is the solution choscn in the Russian SBAS, SDCM. On the other hand. PRN dynamic mask is one of the options considered for multi-constellation augmentation in the SBAS standard evolution. For multi constellation augmentation, it is now possible to configure magicSBAS to change the PRN mask dynamically, with updates in the range of the hour. The new masks are automatically computed m order to maximize the performance at the worst user location in the service region.- B: Connection to real time standardized servers providing precise satellite orbits and clocks: magicSBAS can now optionally connect to RTCM servers providing real time precise orbits and clocks initially devised for real time PPP. After the appropriate re-synchronisation to the SBAS Network Time scale the corrections are used to fill in the fast and long term correction messages, whilst the integrity bound. UDRE, is computed with respect to the broadcast corrections using raw measurements from the dedicated network of reference stations. In case of connectivity problems to the orbits and clocks server, the internally computed corrections are used instead in order to grant the availability of the service. magicSBAS can be configured to assume that the external corrections are L 1 C/A, to use externally provided inter-signal biases, or to do their own computation of the biases. In particular, magicSBAS has been successfully integrated with GMV'sproprietary real time PPP servers, namely magicPPP and IGS Real Time Service. The advantages of using external orbit and clock servers are manifold:- B. 1 : Exploitation of synergies with other services, such as real tune PPP.- B. 2: Analysis of feasibility to meet tail-distribution accuracy requirements for demanding services, such as LPV-200, and, likely, Autoland. This is a key issue for L 1/L5 updates. due to the substantial changes in the error budget, in particular regarding the noise amplification when the signals are combined to build an iono-frec psetidorange.- B.3: It opens the door to the design of lighter SBAS systems, with the accuracy corrections obtained from external organizations complemented with a light dedicated infrastructure to ensure integrity.- C: Enhanced connectivity to real time sources of GNSS reference stations: After the latest update, magicSBAS is able to connect simultaneously to different sources of standardised real time GNSS reference station data. such as NTR1P. EGNOS EDAS and ESA's SPEED-RDS.- D: Enhanced operational capabilities: The logged data can be used for replay or fast replay in the offline version of the test bed. In addition, the architecture of the real time version of magicSBAS has been enhanced so that now it is possible to configure it to run in an inexpensive platform or distributed in dedicated servers to separate essential and non-essential services.These changes have been implemented on top of the existing capabilities of magicSBAS such as configurability of M127 or M128 single or multi constellation augmentation, use of a non -augmented GNSS constellation for ionosphere estimation, single- or dual -frequency solutions, enhanced ionospheric estimation algorithms, exhaustive internal data logging, broadcast via internet or connectivity to uplink stations... Considering the pre-existing and new functionalities, magicSBAS is an invaluable tool for SBAS systems engineering and SBAS standardisation evolution analyses.This paper provides a general introduction to magicSBAS with a description of the pre-existing functionalitics, details the new capabilities introduced, and shows examples of the performances achieved with real data.