SBAS CAT-I Capability in Europe: The LPV-200 Service

C. Hernando, A. Marquez, P. Pintor, R. Roldán, J.M. Álvarez, J.M. Lorenzo

Abstract: The European Geostationary Navigation Overlay Service (EGNOS) is the pan-European Satellite Based Aaugmentation System (SBAS). EGNOS provides an augmentation service to the Global Positioning System (GPS) Standard Positioning Service (SPS). Presently, EGNOS augments GPS using the L1 (1575.42 MHz) Coarse/Acquisition (C/A) civilian signal function by providing correction data and integrity information for improving positioning, navigation and timing services over Europe. EGNOS makes existing satellite navigation signals suitable for safety critical applications. The EGNOS Safety of Live (SoL) service provides enhanced and guaranteed performance and features an integrity warning system which makes it available for safety-critical transport applications, namely in civil aviation; but may support also applications in other SoL domains where lives could be endangered if the performance of the navigation system is degraded below specific accuracy limits without giving notice in the specified time to alert. So, the operational use of the EGNOS SoL Service is defined under a regulated framework and may require specific authorisation by the relevant authorities in the application sectors concerned. This SoL service is provided openly and is freely accessible without any direct charge. The first and main objective of the EGNOS SoL Service is to support civil aviation operations down to LPV (Localizer Performance with Vertical guidance) minima. The EGNOS SoL service is thus compliant with the aviation APV-I (Approach with Vertical Guidance) requirements, as defined by ICAO International Standards and Recommended Practices (SARPS) Annex 10 . It was officially declared available for aviation the 2nd March 2011. EGNOS currently supports civil aviation operations for different PBN Navigation Specifications including en route, arrival, approach and departure flight phases. Notably For the approach phase, EGNOS provides service for the following Instrument Approach Procedures: • NPA (Non-Precision Approaches): LP Localizer Performance, lateral guidance only (RNP APCH operations down to LP minima). • APV (Approaches with Vertical Guidance): LPV Localizer Performance with Vertical guidance, both lateral and vertical guidance (RNP APCH operations down to LPV minima). Currently, Localizer Performance with Vertical guidance (LPV) are the highest precision GNSS (EGNOS enabled) aviation Instrument Approach Procedures. By the use of the current EGNOS SoL service, the pilot can take the aircraft down "blind", without visual contact to the ground, to as low as 250 feet minima (APV, ILS look-alike approach) with a ground infrastructure limited to runway lighting. This paper will provide an overview of the roadmap outlined in the fourth edition of the Global Air Navigation Plan (ICAO Doc 9750, GANP) for the implementation plans of navigation capabilities and GNSS elements, and in particular SBAS that is recognized as a technical enabler for PBN and Precision Approach CAT I/II/III. EGNOS is in constant evolution and the new EGNOS system release V2.4.1M, which will be deployed in summer 2015, will enable LPV operations based on EGNOS SoL service down to a decision height of 200 ft minima (Precision Approach, SBAS CAT-I capability according to the new ICAO Approach Classification in force since November 2014), bringing extra operational benefits and increased accessibility to European runways with respect to APV. This new service level will be called LPV-200 and its declaration towards users is foreseen by the end of 2015. LPV-200 defines its own series of more stringent performance requirements such as Vertical accuracy (VNSE) of 4 m (95%) and Vertical Alarm Limit (VAL) of 35m. In addition, some requirements are defined relative to the probability that the VNSE exceeds 10m in nominal conditions, set to 10-7/per approach, or 15m in degraded conditions, defined as 10-5/per approach. Horizontal accuracy, Integrity risk, Time to Alert, Continuity and Availability performance requirements are as per APV-I service level. These requirements relative to the maximum VNSE are novel with respect to APV-I requirements and whenever they are violated it is said that an Accuracy Major Event (AME) takes place. It is to be noted that the violation of any of the two requirements (VNSE>10 m in nominal conditions or VNSE>15m in degraded conditions) is formally considered as a major event from a safety point of view. For the first time, EGNOS faces these stringent requirements on the accuracy distribution tail of the user vertical position error (VNSE) which are usually reserved to integrity and continuity performances. GSA as the EGNOS Programme Manager and ESSP SAS as the EGNOS Service Provider are keen to provide this new LPV200 service for potential users. However, LPV200 demands a novel statistical characterization of VNSE accuracy distribution tails in line with ICAO requirements and AME represent a new field in the continuous measurement and analysis of SBAS performance. LPV200 requires the development of a new methodology and new tools for performance monitoring of AME and the corresponding VNSE accuracy tails. This is a new challenge in the terms of SBAS performance characterization and reporting. This paper presents a summary of the different activities performed by ESSP, relative to the monitoring, analysis and reporting of EGNOS performance for LPV200 service declaration, as a key element of the EGNOS service provision, and some preliminary results which support the activities done by the industry as part of the EGNOS system release V2.4.1M qualification. Moreover, this paper assesses the impact on the EGNOS service provision and on operational use of the LPV-200 service level for instrument approaches. In particular, this paper provides a complete overview on how the introduction of the new LPV-200 capability will impact any of the operational actors who will take advantage of its performances for aviation applications with respect to the APV approach conditions. The LPV-200 concept of operations is described and the impact at operational level of LPV-200 on • Regulatory framework; • Air Navigation Service Providers (ANSPs); • Aircraft operators; • Aerodrome infrastructure; is explained. The paper will finally identify the challenges for the future to enable the exploitation of the full potential of EGNOS based operations in aviation. In particular the challenge of the introduction of LPV approaches (considered as instrument approaches) to non-instrument runways is to be faced in the coming years across Europe. There are also a number of areas of research on future SBAS-based applications such as surveillance, advanced and rotorcraft instrument approach procedures, timing or safety.
Published in: Proceedings of the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2015)
September 14 - 18, 2015
Tampa Convention Center
Tampa, Florida
Pages: 1565 - 1595
Cite this article: Hernando, C., Marquez, A., Pintor, P., Roldán, R., Álvarez, J.M., Lorenzo, J.M., "SBAS CAT-I Capability in Europe: The LPV-200 Service," Proceedings of the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2015), Tampa, Florida, September 2015, pp. 1565-1595.
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