AUGUR: Pre-Flight Planning for GNSS Operations

AUGUR: Pre-Flight Planning for GNSS Operations

Part of a pilot’s duty is to check if an approach aid will be available at his destination airport, to ensure that landing is possible. This gets a little more complicated if the navigation aid is orbiting in the sky. AUGUR takes into account scheduled maintenance actions on satellites and informs operators if these have an impact on availability. Some ANSPs provide GPS RAIM predicted unavailability in the format of NOTAM and AUGUR supports such service on demand.

AUGUR is a web-based tool which checks the availability of GPS integrity (RAIM) for operations including RNAV 1, RNP 1 and RNP APCH to LNAV and LNAV/VNAV minima.

AUGUR provides the following functions to support operations:

  • the “terminal” function for TMA where GPS-based RNAV 1 or RNP 1 procedures are published; and
  • the “approach” function for airports where RNP APCH to LNAV and LNAV/VNAV minima lines are published.

This allows airspace users to be informed about the number of operational satellites and provides a means by which the availability of GPS integrity can be confirmed for an intended flight.

From 1 July 2012, AUGUR coverage is limited to ECAC airspace only.

This software tool was developed by EUROCONTROL to meet the following requirements:

  • Sub-section 5.2 (Normal Procedures) of Section 5 (Operational Criteria For Use Of GPS Stand-Alone Equipment) of EASA AMC 20-4 (Airworthiness Approval and Operational Criteria For the Use of Navigation Systems in European Airspace Designated For Basic RNAV Operations), which states:

Given a GPS constellation of 23 satellites or less (22 or less for GPS stand-alone equipment that incorporates pressure altitude aiding), the availability of GPS integrity (RAIM) should be confirmed for the intended flight (route and time). This should be obtained from a prediction program either ground-based, or provided as an equipment function or from an alternative method that is acceptable to the Authority.

Dispatch should not be made in the event of predicted continuous loss of RAIM of more than 5 minutes for any part of the intended flight.

  • Sub-section (Pre-flight Planning) of JAA TGL 10 (Airworthiness And Operational Approval For Precision RNAV Operations In Designated European Airspace), which states:

If a stand-alone GPS is to be used for RNAV 1, the availability of RAIM must be confirmed with account taken of the latest information from the US Coastguard giving details of satellite non-availability.

-  Note: RAIM prediction may be a function of the equipment provided that satellite non-availability data can be entered. In the absence of such a function, an airspace service provider may offer an approved RAIM availability service to users.

  • Sub-section 1.1.f (Pre-flight planning) of Appendix 4 (Operational Procedures) to EASA AMC 20-27 (Airworthiness Approval and Operational Criteria for RNP APPROACH (RNP APCH) Operations Including APV BARO-VNAV Operations) states:

For those GNSS systems relying on RAIM, its availability 15 min before Estimated Time of Arrival (ETA) until 15 min after ETA should be verified during the preflight planning. In the event of a predicted continuous loss of fault detection of more than five (5) minutes, the flight planning should be revised (e.g. delaying the departure or planning a different approach procedure).

Note 1: For certain a system, prediction is not systematic but is only required in specific cases and shall be detailed in the relevant section of the AFM.

Note 2: RAIM availability prediction services may be provided to users by the air navigation service provider (ANSP), an avionics manufacturer or other entities.

AUGUR supports GPS RAIM NOTAM services provided by national NOTAM offices.  It gives NOTAM proposals containing GPS RAIM unavailability periods at destination airports where RNP APCH to LNAV and LNAV/VNAV minima will be flown. Requests for this can be made via the EAD service desk.  GPS RAIM predictions by AUGUR are also made available as a data service through an application programming interface (API).  For information and documentation on this service please consult the 'Help' on the AUGUR website.

Finally, AUGUR proposes two additional functions:

  • GPS Status Tool – this provides the number of satellites in the GPS constellation and any outages planned in the coming 72 hours (based on NANUs).


AUGUR is freely accessible.  Click here to access the tool.

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