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􀀴Air Navigation Bureau
􀀴Standards, Recommended Practices (SARPs)
ATMB–CAAC Workshop on GNSS Beijing, 16-17 April 2007
Introduction - ICAO
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ATMB–CAAC Workshop on GNSS Beijing, 16-17 April 2007
Introduction – GNSS
􀀴 The theoretical definition:
􀂾 “GNSS. A worldwide position and time determination system
that includes one or more satellite constellations, aircraft
receivers and system integrity monitoring, augmented as
necessary to support the required navigation performance for
the intended operation.” [from ICAO Annex 10, Volume I]
􀀴 The practical foundation:
􀂾 1994/1996: US and Russia offer to ICAO to provide GPS (Global
Positioning System)/GLONASS (GLObal NAvigation Satellite
System) service for the foreseeable service on a continuous
worldwide basis and free of direct user fees
ATMB–CAAC Workshop on GNSS Beijing, 16-17 April 2007
GNSS developments in ICAO
􀀴 1991: 10th Air Navigation Conference:
􀂾 The Air Navigation Commission requests the initiation of an agreement
between ICAO and GNSS-provider States concerning quality and
duration of GNSS
􀀴 1993: ICAO GNSS Panel established
􀂾 Primary task: to develop SARPs in support of aeronautical applications
of GNSS
􀀴 1994/1996: GPS/GLONASS offers from US/Russia
􀀴 1999: GNSSP completes the development of GNSS SARPS (applicable
2001)
􀀴 2002 – today: GNSSP (subsequently renamed NSP) develops GNSS
SARPs enhancements
􀀴 2003: 11th Air Navigation Conference:
􀂾 The Conference recommends a worldwide transition to GNSS-based air
navigation
ATMB–CAAC Workshop on GNSS Beijing, 16-17 April 2007
ICAO policy on GNSS
􀀴 1994: Statement of ICAO policy on CNS/ATM systems implementation and
operation approved by the ICAO Council:
􀂾 “GNSS should be implemented as an evolutionary progression from
existing global navigation satellite systems, including the United States’
GPS and the Russian Federation’s GLONASS, towards an integrated
GNSS over which Contracting States exercise a sufficient level control
on aspects related to its use by civil aviation. ICAO shall continue to
explore, in consultation with Contracting States, airspace users and
service providers, the feasibility of achieving a civil, internationally
controlled GNSS”
􀀴 1998: Assembly resolutions A32-19 (“Charter on the Rights and Obligations
of States Relating to GNSS Services”) and A32-20 (“Development and
elaboration of an appropriate long-term legal framework to govern the
implementation of GNSS”)
ATMB–CAAC Workshop on GNSS Beijing, 16-17 April 2007
The GPS/GLONASS offers
􀀴 GPS offer (1994):
􀂾 GPS standard positioning service to be made available on a
continuous worldwide basis and free of direct user fees for the
foreseeable future. At least 6 years notice prior to termination.
􀀴 GLONASS offer (1996):
􀂾 GLONASS standard accuracy channel to be provided to the
worldwide aviation community for a period of at least 15 years
with no direct charges collected from users.
􀀴 Both offers accepted by ICAO Council
􀀴 Offers reiterated at various occasions, most recently February 2007
(180th Session of the ICAO Council)
ATMB–CAAC Workshop on GNSS Beijing, 16-17 April 2007
Basic technical principles (1)
􀀴 The aircraft computes its position by “trilateration”
􀀴 A simplified geometrical explanation:
􀂾 the aircraft computes distances d1, d2 and d3 from three
satellites whose positions P1, P2 and P3 are known;
􀂾 knowing distances from, and positions of, three satellites,
it is a simple geometrical problem to derive the position of
the aircraft:
􀂾 the position of the aircraft is the intersection of the three spheres of
radius d1, d2 and d3 and centers respectively P1, P2 and P3
􀂾 (there are actually two intersection points, but typically only one of
them is “reasonable”)
ATMB–CAAC Workshop on GNSS Beijing, 16-17 April 2007
Basic technical principles (2)
􀀴 How does the aircraft know the position of the satellites?
􀂾 the satellite position information is broadcast by the satellites themselves
as a part of the navigation message transmitted by each satellite
􀀴 How does the aircraft compute its distance from the satellites?
　
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