One main use of the system is in aviation.Īccording to specifications, horizontal position accuracy when using EGNOS-provided corrections should be better than seven metres. Ground stations determine accuracy data of the satellite navigation systems and transfer it to the geostationary satellites users may freely obtain this data from those satellites using an EGNOS-enabled receiver, or over the Internet. The system will supplement Galileo in a future version.ĮGNOS consists of 40 Ranging Integrity Monitoring Stations, 2 Mission Control Centres, 6 Navigation Land Earth Stations, the EGNOS Wide Area Network (EWAN), and 3 geostationary satellites. Currently, it supplements the GPS by reporting on the reliability and accuracy of their positioning data and sending out corrections. Typically, LNAV procedures achieve a minimum descent altitude (MDA) of 400 feet height above the runway.The European Geostationary Navigation Overlay Service ( EGNOS) is a satellite-based augmentation system (SBAS) developed by the European Space Agency and EUROCONTROL on behalf of the European Commission.
LNAV approaches are less precise (556m lateral limit) and therefore usually do not allow the pilot to descend to as low an altitude above the runway. Instead, when the aircraft reaches the final approach fix, the pilot descends to a minimum descent altitude using the barometric altimeter. On an LNAV approach, the pilot flies the final approach lateral course, but does not receive vertical guidance for a controlled descent to the runway. GPS NPA (LNAV) refers to a Non-Precision Approach (NPA) procedure which uses GPS and/or SBAS for Lateral Navigation (LNAV). The decision altitudes on these approaches are usually 350 feet above the runway. When the pilot flies an LNAV / VNAV approach, lateraland vertical guidance is provided to fly a controlled descent and a safer maneuver to the runway. Aircraft that don’t use SBAS for the vertical guidance portion must have a Baro-VNAV system, which are typically part of a flight management system (FMS). LNAV / VNAV approaches use lateral guidance (556m lateral limit) from GPS and/or SBAS and vertical guidance provided by either the barometric altimeter or SBAS.
The MDA for the LP approach is expected to be nominally 300 to 400 feet above the runway. LP approaches can only be flown by aircraft equipped with SBAS Avionics receivers. These approaches are needed at runways where, due to obstacles or other infrastructure limitations, a vertically guided approach (LPV or LNAV/VNAV) cannot be published. Localizer Performance (LP) is a recent non-precision approach (NPA) procedure that uses SBAS precision of LPV for lateral guidance and barometric altimeter for minimum descent altitude (MDA) guidance. There are over 2,327 LPV approaches in use today and the FAA is publishing over 500 new LPV approaches per year. LPV approaches are operationally equivalent to the legacy instrument landing systems (ILS), but are more economical because no navigation infrastructure is required at the runway. It is similar to LNAV/VNAV except it is much more precise (40m lateral limit), enables descent as low as 200-250 feet above the runway and can only be flown with an approved SBAS Avionics receiver.
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