mitre-continuity of navigation using gps and sbas v3
TRANSCRIPT
-
8/2/2019 MITRE-Continuity of Navigation Using GPS and SBAS v3
1/16
2006 The MITRE Corporation. All rights reserved.
Continuity of Navigation usingGPS and SBAS
Presentation for GIT/9Daniel OLaughlin
Dr. S.V. Massimini
April 2006
-
8/2/2019 MITRE-Continuity of Navigation Using GPS and SBAS v3
2/16
2006 The MITRE Corporation. All rights reserved.2
Continuity and Availability
The ARNFS gave extensive results on the availabilityofvarious navigation services in the Asia-Pacific Region
GPS
SBAS
GBAS
GRAS
The ARNFS did not include information on the continuityof navigation operations
Limited capability to model continuity until recently
Objective of this briefing is to familiarize the GIT onaspects of continuity of navigation
Will use recently completed results from Alaska, USA
Later efforts may include results for Asia Pacific
-
8/2/2019 MITRE-Continuity of Navigation Using GPS and SBAS v3
3/16
2006 The MITRE Corporation. All rights reserved.3
What are Continuity of Service and
Availability of Service?
Continuityof service is the probability that service will stay
up over a given time span (given that it was up at thebeginning)
Often given as 1 continuity (probability that theservice will fail over a given time span)
Availabilityis the probability that the service is up ifsampled at a random time ( = ratio of up time to total time)
Impact of navigation service unavailability varies withapplication
Time period
-
8/2/2019 MITRE-Continuity of Navigation Using GPS and SBAS v3
4/16
2006 The MITRE Corporation. All rights reserved.4
More Continuity Definitions
Continuity Risk = (1 Continuity)
Average Continuity Risk = the Continuity Risk at a user location
averaged over 24 hours
Two types of continuity risk are computed:
PredictedContinuity Risk: Continuity risk associated withpredicted outages (i.e., those known beforehand) e.g., planned
satellite outages for maintenance, geometric outages, etc. For GPS receivers, predicted continuity risk can be avoided if RAIM
predictionsare used in flight planning (with NOTAM updates)
For WAAS receivers, predicted continuity risk can be avoided bychecking WAAS NOTAMs
UnpredictedContinuity Risk: Continuity risk associated withunpredicted outages e.g., satellite or ground equipment failures
Only en routecontinuity risk is computed for this presentation
Horizontal Alert Limit = 2 nmi
Terminal, NPA, and LPV continuity risk can be computed
-
8/2/2019 MITRE-Continuity of Navigation Using GPS and SBAS v3
5/16
2006 The MITRE Corporation. All rights reserved.5
ICAO Continuity Requirements
(Annex 10 Table 3.7.2.4-1)
-
8/2/2019 MITRE-Continuity of Navigation Using GPS and SBAS v3
6/16
2006 The MITRE Corporation. All rights reserved.6
Assumed Receiver Types
GPS Only (e.g., TSO C129/129A and STC-based)
With and without Baro Aiding
With baro aiding, the standard deviation of pressure altitudeerror was assumed to be 290 m, consistent with aircraft at10,000 ft geometric altitude (see TSO C-129A)
Avionics that assume
SA is on
SA is off
Avionics capable of
Fault Detection (FD) only,
Fault Detection and Exclusion (FDE)
2 and 7.5 degree user mask angle GPS with SBAS (WAAS) (e.g., TSO C145A/146A-based)
With the current WAAS architecture
With the Full LPV Performance WAAS architecture (~2008)
-
8/2/2019 MITRE-Continuity of Navigation Using GPS and SBAS v3
7/16
2006 The MITRE Corporation. All rights reserved.7
Modeling Assumptions
These results are from computer models, and aredependent upon a number of assumptions
Changes in assumptions can produce different results
Changes in location can produce different results
Asia-Pacific results could be different than Alaska But do not anticipate major differences
These results do not include any effects of alternative
navigation or inertial navigation systems
-
8/2/2019 MITRE-Continuity of Navigation Using GPS and SBAS v3
8/16
2006 The MITRE Corporation. All rights reserved.8
Assumed User Locations
6
5
4
3
2
1
User
-13557.5
-14560
-16060
-152.565
-14570
-16070
LongLat21
4
3
6
5
-
8/2/2019 MITRE-Continuity of Navigation Using GPS and SBAS v3
9/16
2006 The MITRE Corporation. All rights reserved.9
Summary of Results:
GPS-Only Avionics, 2Mask Angle
Results Shown are for the24 GPS Martinez Constellation (Appendix B of RTCA DO-229C)
with GPS IFOR Threshold Parameters(values shown are for the worst of the 6 user locations in AK)
< 10-1
< 10-2
< 10-3
< 10-4
< 10-5
< 10-1
< 10-2
< 10-3
< 10-4
< 10-5
AveragePredictedContinuity
Risk per hour
AverageUnpredictedContinuity
Risk per hourAvailabilityBaro-AidingFD/FDE
AvionicsAssumption
on SA(On/Off)Case
Baro
No-Baro
Baro
No-Baro
Baro
No-Baro
Baro
No-Baro
1.7404E-038.4165E-079.9985E-01FDEOff8
5.3723E-032.6370E-069.9958E-01FDEOff7
1.7404E-031.1474E-049.9985E-01FDOff6
5.3723E-031.1631E-049.9958E-01FDOff5
2.6671E-031.1455E-069.9978E-01FDEOn4
9.1607E-034.1592E-069.9914E-01FDEOn3
2.6671E-031.1501E-049.9978E-01FDOn2
9.1607E-031.1765E-049.9914E-01FDOn1
Pass =>
Pass =>
Pass =>Pass =>
-
8/2/2019 MITRE-Continuity of Navigation Using GPS and SBAS v3
10/16
2006 The MITRE Corporation. All rights reserved.10
Summary of Results:
GPS-Only Avionics , 2Mask Angle
Results Shown are for the Current (Nov 2005) Constellation withNo Failures
(values shown are for the worst of the 6 user locations in AK)
< 10-1
< 10-2
< 10-3
< 10-4
< 10-5
< 10-1
< 10-2
< 10-3
< 10-4
< 10-5
AveragePredictedContinuity
Risk per hour
AverageUnpredictedContinuity
Risk per hourAvailabilityBaro-AidingFD/FDE
AvionicsAssumption
on SA(On/Off)Case
8.5726E-064.8780E-061.0000E+00BaroFDEOff16
8.0248E-021.4629E-059.9306E-01No-BaroFDEOff15
8.5726E-061.1828E-041.0000E+00BaroFDOff14
8.0248E-021.2684E-049.9306E-01No-BaroFDOff13
1.4286E-058.1294E-061.0000E+00BaroFDEOn12
8.0246E-021.3014E-059.8264E-01No-BaroFDEOn11
1.4286E-051.2114E-041.0000E+00BaroFDOn10
8.0246E-021.2542E-049.8264E-01No-BaroFDOn9
Pass =>Pass =>
Pass =>Pass =>
-
8/2/2019 MITRE-Continuity of Navigation Using GPS and SBAS v3
11/16
2006 The MITRE Corporation. All rights reserved.11
Summary of Results:
GPS-Only Avionics , 7.5Mask Angle< 10-1
< 10-2
< 10-3
< 10-4
< 10-5
< 10-1
< 10-2
< 10-3
< 10-4
< 10-5
Results Shown are for the24 GPS Martinez Constellation (Appendix B of RTCA DO-229C)
with GPS IFOR Threshold Parameters(values shown are for the worst of the 6 user locations in AK)
AveragePredictedContinuity
Risk per hour
AverageUnpredictedContinuity
Risk per hourAvailabilityBaro-AidingFD/FDE
AvionicsAssumption
on SA(On/Off)Case
Baro
No-Baro
Baro
No-Baro
Baro
No-Baro
Baro
No-Baro
1.3339E-021.3053E-059.9765E-01FDEOff8
6.3118E-023.4805E-059.9434E-01FDEOff7
1.3339E-021.2546E-049.9765E-01FDOff6
6.3118E-021.4455E-049.9434E-01FDOff5
4.9706E-021.7337E-059.9684E-01FDEOn4
7.3740E-024.1132E-059.8742E-01FDEOn3
4.9706E-021.2922E-049.9684E-01FDOn2
7.3740E-021.5010E-049.8742E-01FDOn1
Pass =>Pass =>
Pass =>Pass =>
-
8/2/2019 MITRE-Continuity of Navigation Using GPS and SBAS v3
12/16
2006 The MITRE Corporation. All rights reserved.12
Summary of Results:
GPS-Only Avionics , 7.5Mask Angle
Results Shown are for the Current (Nov 2005) Constellation withNo Failures
(values shown are for the worst of the 6 user locations in AK)
< 10-1
< 10-2
< 10-3
< 10-4
< 10-5
< 10-1
< 10-2
< 10-3
< 10-4
< 10-5
AveragePredictedContinuity
Risk per hour
AverageUnpredictedContinuity
Risk per hourAvailabilityBaro-AidingFD/FDE
AvionicsAssumption
on SA(On/Off)Case
Baro
No-Baro
Baro
No-Baro
Baro
No-Baro
Baro
No-Baro
4.1255E-021.3509E-059.9306E-01FDEOff8
1.1875E-014.6642E-059.7917E-01FDEOff7
4.1255E-021.2586E-049.9306E-01FDOff6
1.1875E-011.5494E-049.7917E-01FDOff5
4.1269E-022.1692E-059.9306E-01FDEOn4
1.5407E-015.3607E-059.6181E-01FDEOn3
4.1269E-021.3304E-049.9306E-01FDOn2
1.5407E-011.6105E-049.6181E-01FDOn1
Pass =>Pass =>
Pass =>Pass =>
-
8/2/2019 MITRE-Continuity of Navigation Using GPS and SBAS v3
13/16
2006 The MITRE Corporation. All rights reserved.13
Summary of Results:
WAAS Avionics< 10-1
< 10-2
< 10-3
< 10-4
< 10-5
< 10-1
< 10-2
< 10-3
< 10-4
< 10-5
AveragePredictedContinuity
Risk per hour
AverageUnpredictedContinuity
Risk per hourAvailabilityGPS
ConstellationWAAS
ArchitectureCase
1.7573E-039.5395E-069.9985E-0128 CurrentFLP4
7.0105E-033.7977E-059.9942E-0128 CurrentCurrent3
5.1555E-047.7215E-069.9993E-0124 MartinezFLP2
3.1815E-035.1937E-059.9914E-0124 MartinezCurrent1Pass =>
Pass =>
Pass =>
Pass =>
-
8/2/2019 MITRE-Continuity of Navigation Using GPS and SBAS v3
14/16
2006 The MITRE Corporation. All rights reserved.14
Observations (1 of 2)
Predicted continuity risk
With a Pre-flight check (GPS-only avionics) or checkingWAAS NOTAMs (WAAS avionics)
User would be subjected to only predictedcontinuity losses
Without a Pre-flight check (GPS avionics) or check of WAASNOTAMs
User would be subjected to predicted and unpredictedlosses
GPS-only avionics generally have higher rates of predictedcontinuity risk (~10-1 - 10-2 per hour) than WAAS avionics(~10-3 - 10-4 per hour)
-
8/2/2019 MITRE-Continuity of Navigation Using GPS and SBAS v3
15/16
2006 The MITRE Corporation. All rights reserved.15
Observations (2 of 2)
Unpredicted continuity risk
For GPS-only avionics, unpredicted continuity risk is lowerfor avionics that perform FDE (~10-5 per hour) than thosethat do not (>~10-4 per hour)
For WAAS avionics, unpredicted continuity loss is ~10-5 to~10-6 per hour
-
8/2/2019 MITRE-Continuity of Navigation Using GPS and SBAS v3
16/16
2006 The MITRE Corporation. All rights reserved.16
Conclusions
GPS avionics without FDE do not meetICAO en-routecontinuity requirements
Note that GPS with other navigation aids may be OK
This is why GPS alone is considered supplemental
GPS avionics with FDE meetICAO en-route continuityrequirements
Pre-flight RAIM check must be accomplished
May not be able to depart if RAIM check is not satisfactory
US currently authorizes GPS with FDE as primary meansnavigation in remote areas (with preflight RAIM check)
WAAS avionics meetICAO en-route continuityrequirements
WAAS NOTAMs must be checked
US currently authorizes WAAS as primary means navigation
(with preflight NOTAM check)