Transcript Navigating eLoran: Challenges and the Way Forward

The importance of resilient
position-fixing for e-Navigation
George Shaw
PNT Seminar, RNN, Stockholm
18 May 2011
Resilient PNT: a role for eLoran?
 Maritime dependence on GPS
 GNSS vulnerabilities
- GLA ship trials of GPS jamming
- Space weather / ionospheric scintillation
 Public awareness / media coverage
- Royal Academy of Engineering report
 Options for maritime Resilient PNT
- The case for eLoran
 eLoran: status & wider benefits
Visual Signalling
 Bell Rock Lighthouse celebrates
200 years
 Lights & buoys are crucial…
 … now and in future for
navigation close-to-danger
 But GPS has become the
principal maritime Aid-toNavigation…
Source: Northern Lighthouse Board
GLA DGPS augmentation for
accuracy and integrity
The GLAs operate 14 DGPS stations
e-Navigation needs resilient PNT
 e-Navigation by 2018-2020: “the harmonized collection,
integration, exchange, presentation and analysis of maritime
information ...to enhance berth to berth navigation…”
 IMO says: “e-Navigation systems should be resilient …. robust,
reliable and dependable. Requirements for redundancy,
particularly in relation to position fixing systems should be
considered”
+
≠ resilient PNT
due to GNSS
vulnerability…
Picture Courtesy of US National Executive Committee
Flamborough Head Jamming Trial 2008
AIS radar overlay
included erroneous
positions
Erroneous GPS reported
positions, courses and
speeds
Reference: http://www.gla-rrnav.org/file.html?file=b128b75bbea969dd7c28feb73d02cb63
THV Galatea Trial 2009
 With full denial of the GPS signal, some large position errors
were observed
- Blue ship icon is GPS indicated position
- Green circle is true position (from eLoran): eLoran was unaffected by the
jamming
Reference: http://www.gla-rrnav.org/file.html?file=0968bb9a8ee1ea4ad8c35241ac29c951
THV Galatea Trial 2009
 With higher power jamming, the
GPS position visited some wide
spread locations
 With lower power jamming
comparable to the GPS signal
level caused
- Hazardously Misleading
Information (HMI)
- No alarms sounded
- Erroneous positions and
velocities, some of them
barely noticeable!
‘wide spread locations’
THV Galatea Trial 2009
 With a little more jammer
power, alarms began to
sound
 Eventually all of these
bridge systems failed….
- ECDIS: Electronic Chart
Display
- Ship’s Autopilot
- DGPS: Differential GPS
- Heli-deck stabilisation
system
- DSC-GMDSS: Maritime
Distress Safety System
- Radar
- Gyro-compass
- AIS: Automatic Identification
System
Mitigation of GNSS vulnerability
+
+ ?? = resilient PNT
 Cost Benefit Analysis of alternative PNT options (by 2018 - 20)
 Compared four options
-
Option 1: ‘Do Minimum’
Option 2: Physical and radar Aids-to-Navigation (AtoN)
Option 3: GNSS ‘hardening’ and GNSS monitoring
Option 4: eLoran
 Rigorous business case provided to the UK Department for
Transport in Sept 2010
Option 2: Physical & Radar AtoN
 Enhanced visual AtoN
- e.g. synchronised/sequenced
 ‘New Technology’ radar
 Absolute positioning
 Coastal infrastructure
- Radar reflectors
- Target enhancers
 NT compatible radar
beacons (Racons)
 Independent of GNSS
Option 3: GNSS Hardening
 Multi-constellation GNSS
- GPS, Galileo, GLONASS
- DGNSS infrastructure
 GNSS interference mitigation
- external monitoring
- receiver – advanced RAIM
- robust systems integration
 Integrated SBAS (EGNOS)?
 Sifted out due to 2018 timescale
- adaptive antennas
- inertial augmentation
- signals of opportunity
Integrity
Monitor
Receiver
Reference
Station
Receiver
User
Transmitter
Integrity
Monitor SW
Processing
Reference
Station SW
Processing
Source: NSL
Option 4: eLoran
 Independent, complementary
and dissimilar to GNSS
 Low frequency / high power /
terrestrial
 Modern s/w Rx on powerful h/w
platform available
 Chip-level integration possible
 Meets maritime performance
requirements for coastal and
harbour approach navigation
- accuracy, availability,
integrity, and continuity
Results of Analysis of Options
 eLoran has largest economic return
over 10 to 15 year lifetime
- Balance of physical and radionavigation
AtoN allows removal of some lights
 Other options have negative returns
 Only eLoran has been
demonstrated to provide fully
effective mitigation against the
vulnerability of GNSS
 Allowing full benefits of e-Navigation
for maritime
 Substantial cross-sector benefits
eLoran features – core service
 Precise timing, locked to UTC
- independent of GNSS
- 2-way time satellite transfer (TWTST)
- radically different from Loran-C
 no ‘chains’
 no 2-way time baselines
- supports autonomous control and
monitoring by each nation
 All-in-View receivers
- uses all available transmitters
- single transmitter provides time
- 3 transmitters provide 2D position
and time
 Signal propagation corrections
- Additional Secondary Factors (ASFs)
- compensate for propagation delay over
land
- one-off coastal survey
- database in eLoran receiver
 Differential Loran (DLoran)
- local reference stations for harbour
approach
- real-time corrections for temporal
variations
 eLoran Data Channel (Eurofix)
- integrity alerts within time to alarm
- transmit DLoran corrections
65  N
35+
Ejde

60 N
55  N
30
Vaerlandet
25
Anthorn
20
Sylt
15
50  N
10
Lessay
5
45  N
15  W
10  W

Soustons
5 W
0

5 E

10 E
Loran
Station
DLoran Ref
Station
ASF Map
0
Accuracy, R95 [m]
for noise values not exceeded 95% of the time
eLoran features - augmentation
60km
Source: Williams and Hargreaves, eLoran Performance in the Orkney Archipelago, Proc ILA
38, October 2009, Portland ME, USA
Accuracy: ~10m (95%)
Prototype eLoran on air in Europe with better than 10 metre accuracy
Status of eLoran in the UK
 Prototype eLoran routinely operates
(since 2009)
 Anthorn Tx with >99.9% availability
 Prototype DLoran established in
Harwich (and rapid mobile
deployment, for trials)
 Combined ASFs / DLoran proven
 Initial Operational Capability in 2013
- Covers 6 SOLAS class Channel ports
 Full Operational Capability in 2018
- Covers further 22 SOLAS class ports
European Status of (e)Loran
 9 Loran transmitters operational at
various standards, monitored and
controlled from CCB at Brest
 Informal cooperation since end of
NELS agreement
 No policy to move to eLoran
 European Radio Navigation Plan?
 France: trials of DLoran and study
of TWTST
 Norway: bilateral with Russia for
Loran / Chayka (Tumanny station)
compatibility by 2013
Wider Status of (e)Loran
 US position on a backup for GPS
remains uncertain
- closure of Loran-C (460m 95%)
- consolidation of industry (UrsaNav)
- concept of ‘LF Phoenix’
 Russia: modernisation of Chayka
- planned operation to at least 2020
- eChayka: 7 -20m accuracy, differential
corrections and data channel
 Saudi Arabia
- planned upgrade to eLoran
 FERNS
- Japan decision to withdraw
- S Korea, China, Russia continue
Conclusions
eLoran is only system, when combined with GNSS, that can
achieve resilient PNT by 2018 for maritime e-Navigation
eLoran potential cross-sector benefits of accuracy, integrity,
availability and continuity include seamless PNT information for:
protection of critical national infrastructure
police and emergency services
telecomms / internet
power generation
banking / financial transactions
land-based transport
agriculture
Thank You
For more information contact:
[email protected]