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LORAN-C Friend or Foe? Mike Bedford. British Cave Research Association Cave Technology Symposium 2010 17 th April 2010, Horton-in-Ribblesdale, North Yorkshire. Overview of Presentation. LORAN-C is a radio navigation system intended for marine use. It interferes with cave radios e.g. HeyPhone. - PowerPoint PPT Presentation
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LORAN-CFriend or Foe?
Mike Bedford
British Cave Research AssociationCave Technology Symposium 2010
17th April 2010, Horton-in-Ribblesdale, North Yorkshire
British Cave Research Association - Cave Technology Symposium 201017th April 2010, Horton-in-Ribblesdale, North Yorkshire
Overview of Presentation
• LORAN-C is a radio navigation systemintended for marine use.
• It interferes with cave radios e.g. HeyPhone.• Despite it making communication difficult,
there are some potential benefits for cavers.• Here I provide background on LORAN-C and
discuss possible caving applications.
British Cave Research Association - Cave Technology Symposium 201017th April 2010, Horton-in-Ribblesdale, North Yorkshire
Hyperbolic Navigation (1)
• LORAN-C is a hyperbolicnavigation system.
• Operates by measuringtime distance of arrivalof signals from a pair ofsynchronised transmitters.
Transm itter 1
LO Ps
ExtendedBaseline
Transm itter 2
British Cave Research Association - Cave Technology Symposium 201017th April 2010, Horton-in-Ribblesdale, North Yorkshire
Hyperbolic Navigation (2)
• By using two pairsof transmitters afix can be obtained.
Tx 3
Tx 1 Tx 2
Am bigu ity
British Cave Research Association - Cave Technology Symposium 201017th April 2010, Horton-in-Ribblesdale, North Yorkshire
LORAN-C Frequency
• 100kHz centre frequency• 99% of power within 90-110kHz…• … but high power transmitters• … therefore significant signal at 87kHz• … hence interference for cave radios• Later presentation on a method of preventing
Loran-C interference
British Cave Research Association - Cave Technology Symposium 201017th April 2010, Horton-in-Ribblesdale, North Yorkshire
LORAN-C Chains
• LORAN-C is organised in “chains”• A chain covers a geographical area• Chain comprises master station (M)…• … plus 2 – 4 slaves (W, X, Y, Z)• More than one chain might be detectable• So chains are differentiated by their Group
Repetition Interval (GRI)
British Cave Research Association - Cave Technology Symposium 201017th April 2010, Horton-in-Ribblesdale, North Yorkshire
LORAN-C Timing
M X Y Z M
~200 S1m S 2m S
G R I
ED (X)
ED (Y)
ED (Z)
British Cave Research Association - Cave Technology Symposium 201017th April 2010, Horton-in-Ribblesdale, North Yorkshire
LORAN-C Pulses
0
T i m i n g s f r o m 3 r d z e r o - c r o s s i n g ( 3 0 S )
50 100 150 200
British Cave Research Association - Cave Technology Symposium 201017th April 2010, Horton-in-Ribblesdale, North Yorkshire
Accuracy
• Unlike GPS, LORAN-C accuracy depends on receiver location with respect to transmitters
• Best on baseline between master and slave because LOPs are closer here
• Absolute accuracy 185 – 463m• Repeatable accuracy 18 – 91m• eLORAN improves this to 8 – 20m
British Cave Research Association - Cave Technology Symposium 201017th April 2010, Horton-in-Ribblesdale, North Yorkshire
Underground Performance
• Accuracy inferior to GPS…• … but LORAN-C is available underground• But will signal strength by adequate?• Actually s/n is the most important factor and
less noise underground• Patent Application WO 20061130223 claims
improved s/n underground
British Cave Research Association - Cave Technology Symposium 201017th April 2010, Horton-in-Ribblesdale, North Yorkshire
Underground Accuracy
• Non-uniform geology• Sloping surface topology
• Therefore accuracy possibly degraded
FromM
FromM
FromZ
FromZ
British Cave Research Association - Cave Technology Symposium 201017th April 2010, Horton-in-Ribblesdale, North Yorkshire
Caving Applications
• Accuracy not nearly good enough for normal surveying but…
• … “differential accuracy” may be good enough for “rough and ready” surveying (e.g. new cave on expedition)
• Repeatable accuracy might be good enough to permit its use for underground route finding (a contentious application)
British Cave Research Association - Cave Technology Symposium 201017th April 2010, Horton-in-Ribblesdale, North Yorkshire
Future of LORAN-C (1)
• For years we’ve been expecting LORAN-C to be phased out – good news for cave radio
• LORAN-C was turned off in North America earlier this year
• LORAN-C chains in Europe were transferred from US Navy to host nations in 1995
• Some have closed (e.g. Mediterranean Sea)
British Cave Research Association - Cave Technology Symposium 201017th April 2010, Horton-in-Ribblesdale, North Yorkshire
Future of LORAN-C (2)
• North East Europe chainswere managed by NELS
• NELS agreement terminated in 2005• However, ad hoc arrangement still exists
between host nations and most are committed to continuation in the mid term
• Stations being upgraded to eLORAN
British Cave Research Association - Cave Technology Symposium 201017th April 2010, Horton-in-Ribblesdale, North Yorkshire
Chayka
• Chayka was developed by USSR• Similar to LORAN-C• Same frequency but different pulse shape• Russian Chayka chains also remain operational• West Russia chain available in Eastern Europe• Some Loran-C receivers also use
Chayka signals
British Cave Research Association - Cave Technology Symposium 201017th April 2010, Horton-in-Ribblesdale, North Yorkshire
Former NELS ChainsTransmitter Designation
Emission Delay (µS) Location Country
Coordinates Power (kW) Latitude Longitude
Lessay 6731 Chain
M Lessay France 49°08′55.224″N 01°30′17.029″W 250
X 13,000 Soustons France 43°44′23.099″N 01°22′49.584″W 250
Y 27,300 Anthorn UK 54°54′41.949″N 03°16′42.587″W 250
Z 42,100 Sylt Germany 54°48′29.975″N 08°17′36.856″E 250
Bø 7001 Chain
M Bø Norway 68°38′06.216″N 14°27′47.350″E 400
X 14,100 Jan Mayen Norway 70°54′51.478″N 08°43′56.525″W 250
Y 29,100 Berlevåg Norway 70°50′43.014″N 29°12′15.980″E 250
Eiði 9007 Chain
M Eiði Faroe 62°17′59.837″N 07°04′26.079″W 400
W 14,200 Jan Mayen Norway 70°54′51.478″N 08°43′56.525″W 250
X 28,000 Bø Norway 68°38′06.216″N 14°27′47.350″E 400
Y 41,100 Værlandet Norway 61°17′49.435″N 04°41′46.618″E 250
Sylt 7499 Chain
M Sylt Germany 54°48′29.975″N 08°17′36.856″E 250
X 14,100 Lessay France 49°08′55.224″N 01°30′17.029″W 250
Y 29,500 Værlandet Norway 68°38′06.216″N 14°27′47.350″E 250
British Cave Research Association - Cave Technology Symposium 201017th April 2010, Horton-in-Ribblesdale, North Yorkshire
Former NELS & Chayka Chains
Rugby
Jan Mayen
Lessay
Soustons
Berlevåg
Sim feropol
SlonimKarachev
Petrozavodsk
Bø
Væ rlandetEi ið
Sylt
British Cave Research Association - Cave Technology Symposium 201017th April 2010, Horton-in-Ribblesdale, North Yorkshire
Where Next?
• LORAN-C receivers are cheap• Former US users off-loading for a few dollars
• Time for some underground experiments?
British Cave Research Association - Cave Technology Symposium 201017th April 2010, Horton-in-Ribblesdale, North Yorkshire
Thank you for ListeningAny Questions?