Navigating eLoran: Challenges and the Way Forward
Download
Report
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]