[GNSS.UNS] - GNSS not available - coding

Owned by POROSNICU Eduard
Last updated: 2022 Oct 14 by WOJTOWICZ Aleksander

Definition

The predicted unavailability of GNSS services, used for PBN applications in airport (and enroute) environment, may be caused by multiple factors.

  • this scenario enables the encoding of the information about the predicted unavailability (or limited availability) of RAIM and  GBAS/SBAS service or Radio Frequency Interference (colloq. jamming) with GNSS signals at a single aerodrome or in an area;
  • this scenario provides separate encoding paths for aerodrome and enroute area outage indications to simplify data provision and eventually NOTAM generation;
  • the outage or interference of any GNSS service is likely to trigger the unavailability of certain satelliteApproachTypes.

Event data

The following diagrams identify the information items that are usually provided by a data originator for these types of event.

The table below provides more details about each information item contained in the diagrams. It also provides the mapping of each information item within the AIXM 5.2 structure. The name of the variable (first column) is recommended for use as label of the data field in human-machine interfaces (HMI). 


EBNF Code

EBNF code 
input_area_outage = "satellite system" {"satellite navigation service"} ["service outage area"]  "operational status" \n
"start time" "end time" [schedule] \n
[note].

EBNF 
input_aerodrome = ("satellite system" | "GBAS service") "affected aerodrome" {"approach type"} {"runway direction designator"} "operational status" \n
"start time" "end time" [schedule] \n
[note].

aData item

Description

AIXM mapping

satellite system

A satellite system for which the interrupted operation is predicted.

The item is used in combination with other attributes in order to identify the satellite system concerned.

SatelliteSystem.designator
GBAS service

A Ground-based augmentation system for which the interrupted operation is expected.

The item is used in combination with other attributes in order to identify the  system concerned.

GBASService.name
satellite navigation serviceType of aircraft operation supported in a specified service area.SatelliteService.serviceType with the list of values CodeSatelliteNavigationServiceType
service  outage areaThe extent of the area where the satellite navigation service may be affected by predicted interruption.SatelliteService.SatelliteServiceArea/Surface according to the rules for encoding for encoding {{Geometrical and geographical data}}
affected aerodromeA reference (name, designator) to  airport/heliport that for which the predicted satellite navigation service interruption has an operational relevance and needs to be notified to the users thereof.Event.concernedAirportHeliport
approach typeThe type of final approach for which the satellite navigation system is used at the location and may be affected by the predicted outage.SatelliteService.SatelliteApproachOperation.satelliteApproachType with the list of values CodeSatelliteApproachType
runway direction designator

The designator of the runway direction that is served by GBAS.

In combination with other items, this is used to identify the GBAS concerned.

GBASService.servedApproach/RunwayDirection
operational statusThe availability of the service.

SatelliteService.SatelliteApproachOperation.operationalStatus ; SatelliteService.SatelliteServiceArea.operationalStatus or GBASService.NavaidOperationalStatus with values='RAIM_NOT_AVBL' - for predicted RAIM unavailability; =''UNSERVICEABLE'' - for GBAS/SBAS unavailability; ='UNRELIABLE' - for GNSS interference/jamming indication or SBAS ambiguous indications; ='FALSE_INDICATION' or 'FALSE_POSSIBLE' - for GBAS false indications

start time


The effective date & time when the predicted event starts.

SatelliteService/TimeSlice.featureLifetime/beginPosition, SatelliteService/TimeSlice/validTime/beginPosition or GBASService/TimeSlice/validTime/beginPosition and

Event/EventTimeSlice.validTime/beginPosition and Event/EventTimeSlice.featureLifetime/beginPosition

end time

The end date & time when the predicted event ends. It might be an estimated value.

SatelliteService/TimeSlice.featureLifetime/endPosition, SatelliteService/TimeSlice/validTime/endPosition or GBASService/TimeSlice/validTime/endPosition and

Event/EventTimeSlice.validTime/endPosition and Event/EventTimeSlice.featureLifetime/endPosition

schedule

A schedule might be provided, in case the predicted interruption is only active according to a timetable, within the period between the start of life and the end of life.

SatelliteService.SatelliteApproachOperation.operationalStatus/Timesheet/, SatelliteService.SatelliteServiceArea.operationalStatus/Timesheet/ or GBASService.NavaidOperationalStatus/Timesheet/ according to the rules for {{Schedules}}

note

A free text note that provides further instructions concerning the satellite navigation service operational status situation.SatelliteService.annotation or GBASService.annotation with purpose='REMARK'


Assumptions for baseline data

This scenario uses references to AIXM 5.2

The AIXM 5.1(.1) model lacks the capability to code the GNSS core, SBAS and GBAS system characteristics. Therefore, for this scenario, the only viable option is to consider that the baseline data for GNSS core and GBAS/SBAS systems is coded using the new GNSS model provided in AIXM 5.2. This can be implemented as an extension of the AIXM 5.1(.1) model. It should be assumed that all core GNSS/GBAS/SBAS systems are already part of BASELINE data, coded as e.g. SatelliteSystem.type='GNSS', SatelliteSystem.designator='GPS' or SatelliteSystem.type='SBAS', SatelliteSystem.designator='EGNOS'.

Temporary links to the pages explaining the new model:


Data encoding rules

The data encoding rules provided in this section shall be followed in order to ensure the harmonisation of the digital encodings provided by different sources. The compliance with some of these encoding rules can be checked with automatic data validation rules.


Identifier

Data encoding rule

ER-01

The temporary outage of the RAIM service shall be encoded as:

  • a new Event with a BASELINE TimeSlice (scenario=”GNSS.UNS”, version=”2.0”); and
  • a new SatelliteService or GBASService BASELINE associated to SatelliteSystem or GBAS affected by the outage, for which the "event:theEvent" property shall point to the Event instance created above.
ER-02

If the input includes affected aerodrome, then SatelliteService shall include the approachLocation and eventually SatelliteApproachType.

If the input includes affected aerodrome and GBASService then it shall include servedApproach/RunwayDirection.

If the input data includes "service outage area", then SatelliteServiceArea shall be coded.

ER-03

If the Satellite Service status change is limited to a discrete schedule within the overall time period between the "start time" and the "end time", then this shall be encoded using as many as necessary timeInterval/Timesheet properties for the SatelliteApproachOperation.operationalStatus or SatelliteService.SatelliteServiceArea.operationalStatus of their Timeslice. See also the rules for Event Schedules. It is recommended that the HMI of a data provider application allows to provide a schedule only in relation with active times, because only these will be translated into NOTAM text.