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Flying around different parts of Europe, it is apparent that there are a significant number of EGNOS based procedures available. When it comes to approaches, all parts of the continent use the same EGNOS system but for each runway there is a given 5-digit channel number. Which of the following statements is correct?
  • A
    EGNOS covers an extensive area by using geostationary satellites and the channel number is used for approach identification only since EGNOS uses the normal GPS frequency.
  • B
    EGNOS is the European SBAS that is used to improve accuracy and integrity of general GNSS navigation and GBAS is used to augment SBAS when selecting its channel number.
  • C
    EGNOS is the European satellite system running in parallel with GPS but has more satellites, enabling greater accuracy, and the channel number is to tune the receiver to EGNOS.
  • D
    Any GNSS receivers are by default capable of using the EGNOS signals since they use the same frequency as GPS whereas additional equipment is needed to receive GBAS.

Refer to figure.
Learning Objective 062.06.02.02.02: State that the frequency band of the data link is identical to that of the GPS signals.


SATELLITE BASED AUGMENTATION SYSTEMS (SBAS)
SBAS uses the idea of differential GPS (dGPS) and spreads it over very wide area. The satellites involved have geostationary orbits, meaning that they stay over the same place on the Earth all the time, and can reduce GNSS errors and increase integrity over a very large area. This means that there are multiple around the world, WAAS for the USA, EGNOS for Europe, GAGAN for India, MSAS for Japan, etc.


As previously mentioned, EGNOS is the european SBAS, and provides its service using the normal L1 frequency band, the same as the C/A signal for GPS, but obviously contains different data such as the range modifications for each satellite and any integrity and availability messages. SBAS also allows its geostationary satellites to provide another GNSS signal for extra availability, also on that frequency.

The 5 digit code that is individual to each approach procedure is just an identifier code to tell the system which procedure you will be doing, it does not change the frequency band that is picked up.

It is important to note that just because SBAS uses the same frequency band as GPS, receivers are not automatically capable of receiving and processing the extra information provided.

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