eLoran Definition Document for Consultation

Enhanced Loran eLoran Definition Document For Consultation Comments to ILA by 1 April Report Version 01 Report Version Date 12 January 2007 eLoran Definition Document For Consultation Comments to ILA by 1 April Authoring Team Organization Dr Sally Basker General Lighthouse Authorities GLA of the UK and Ireland Commander Joseph Chop US Coast Guard Colonel J Ron Davis USAF Ret Booz Allen Hamilton Captain G Thomas Gunther USCG Ret Booz Allen Hamilton Lieutenant Michael Herring US Coast Guard Mr Francis Hubert DCN Brest France Professor David Last GLA Consultant Dr Sherman Lo Stanford University Commander John Merrill US Coast Guard Lieutenant Kirk Montgomery US Coast Guard Mr Mitchell J Narins US Federal Aviation Administration Commander Christopher Nichols US Coast Guard Dr Gerard Offermans Reelektronika BV Dr Ben Peterson Captain USCG Ret Peterson Integrated Geopositioning Captain Robert Wenzel USCG Ret Booz Allen Hamilton Lieutenant Ronald Wright US Coast Guard Date 12 January 2007 Page 2 of 17 Version 01 01 eLoran Definition Document For Consultation Comments to ILA by 1 April Executive Summary Overview This Enhanced Loran eLoran Definition Document has been published by the International Loran Association to provide a highlevel definition of eLoran for policy makers service providers and users It was developed in November 2006 at the United States Coast Guard Navigation Center by an international team of authors Enhanced Loran is an internationallystandardized positioning navigation and timing PNT service for use by many modes of transport and in other applications It is the latest in the long standing and proven series of lowfrequency LOngRAnge Navigation LORAN systems one that takes full advantage of 21st century technology eLoran meets the accuracy availability integrity and continuity performance requirements for aviation nonprecision instrument approaches maritime harbor entrance and approach maneuvers landmobile vehicle navigation and locationbased services and is a precise source of time and frequency for applications such as telecommunications1 eLoran is an independent dissimilar complement to Global Navigation Satellite Systems GNSS It allows GNSS users to retain the safety security and economic benefits of GNSS even when their satellite services are disrupted The eLoran System eLoran meets a set of worldwide standards and operates wholly independently of GPS GLONASS Galileo or any future GNSS Each users eLoran receiver will be operable in all regions where an eLoran service is provided eLoran receivers shall work automatically with minimal user input The core eLoran system comprises modernized control centers transmitting stations and monitoring sites eLoran transmissions are synchronized to an identifiable publiclycertified source of Coordinated Universal Time UTC by a method wholly independent of GNSS This allows the eLoran Service Provider to operate on a time scale that is synchronized with but operates independently of GNSS time scales Synchronizing to a common time source will also allow receivers to employ a mixture of eLoran and satellite signals The principal difference between eLoran and traditional LoranC is the addition of a data channel on the transmitted signal This conveys applicationspecific corrections warnings and signal integrity information to the users receiver It is this data channel that allows eLoran to meet the very demanding requirements of landing aircraft using nonprecision instrument approaches and bringing ships safely into harbor in lowvisibility conditions eLoran is also capable of providing the exceedingly precise time and frequency references needed by the telecommunications systems that carry voice and internet communications eLoran Service Provision eLoran services are provided by a Core eLoran Service Provider and various Application Service Providers Core eLoran Service Provider delivering a highly precise version of the core signal originally described in the US Coast Guard Specification of the Transmitted LoranC Signal and 1 Lorans Capability to Mitigate the Impact of a GPS Outage on GPS Position Navigation and Time Applications Prepared for the Federal Aviation Administration Vice President for Technical Operations Navigation Services Directorate dated March 2004 Date 12 January 2007 Page 3 of 17 Version 01 eLoran Definition Document For Consultation Comments to ILA by 1 April Application Service Providers eg aviation maritime etc delivering applicationspecific data eg differential Loran messages or early skywave warnings that may be communicated using the eLoran data channel eLorans enhanced accuracy availability integrity and continuity meets the requirements for aviation nonprecision instrument approaches maritime harbor entrance and approach maneuvers landmobile vehicle navigation and locationbased services It also allows absolute UTC time to be recovered with an accuracy of 50 nanoseconds as well as meeting the Stratum 1 frequency standard needed by telecommunications users Accuracy Availability Integrity Continuity 0004 001 nautical mile 8 20 meters 0999 09999 0999999 1 x 107 0999 09999 over 150 seconds Notes 1 Accuracy to meet maritime harbor entrance and approach 2 Availability integrity and continuity to meet aviation nonprecision approach in the US eLoran System Performance Requirements eLoran services will deliver safety security and economic benefits to a wide range of stakeholders eg governments service providers and users eg aviation maritime allowing aviation communications navigation and surveillance functions to migrate to digital communications enabling maritime eNavigation including permanent or temporary virtual AtoNs to be used to mark dangerous waters supporting road user charging providing authentication and maintaining synchronization of wired and wireless telecommunications without the need for expensive external oscillators The Way Ahead eLoran is an independent dissimilar complement to GNSS As such it will allow PNT users with demanding safetycritical or missioncritical applications to secure their safety security and economic benefits even when their satellite services are disrupted eLoran is capable of meeting the accuracy availability integrity and continuity performance requirements for aviation nonprecision instrument approaches maritime harbor entrance and approach maneuvers landmobile vehicle navigation locationbased services and precise time and frequency users This document the first of several needed to fully define the system marks the beginning of an international effort to secure accurate and reliable sources of PNT for 21st century users with demanding safetycritical or missioncritical applications Date 12 January 2007 Page 4 of 17 Version 01 eLoran Definition Document For Consultation Comments to ILA by 1 April Contents 1 Introduction 7 11 Overview 7 12 Background 7 13 Contents 8 2 The eLoran System 8 21 eLoran Signal 9 22 Transmitting Stations 10 23 Control Centers 10 24 Monitor SitesReference Stations 10 25 Users Equipment 10 3 Applications 11 31 Overview 11 32 Aviation 11 33 Maritime 12 34 Land Mobile 14 35 LocationBased Services 14 36 Time Frequency 15 4 eLoran Service Provision 15 41 Documentation 17 5 Conclusion 17 Date 12 January 2007 Page 5 of 17 Version 01 eLoran Definition Document For Consultation Comments to ILA by 1 April Acronyms ADSB Automatic Dependent Surveillance Broadcast aviation AIS Automatic Identification System maritime AtoN Aid to Navigation maritime CNS Communications Navigation Surveillance aviation ECDIS Electronic Chart Display Information System eLoran Enhanced Loran FAA Federal Aviation Administration GLA General Lighthouse Authorities eNavigation Enhanced Navigation maritime GNSS Global Navigation Satellite System GPS Global Positioning System ICAO International Civil Aviation Organization IEC International Electrotechnical Commission IMO International Maritime Organization ITU International Telecommunications Union Loran LOngRAnge Navigation MOPS Minimum Operational Performance Standards PNT Positioning Navigation and Timing PStatic Precipitation Static Ret Retired RNAV Area Navigation aviation RNP Required Navigation Performance SSX Solid State Transmitter UPS Uninterruptible Power Supply US United States of America USCG US Coast Guard UTC Coordinated Universal Time WWRNS World Wide Radionavigation System Date 12 January 2007 Page 6 of 17 Version 01 eLoran Definition Document For Consultation Comments to ILA by 1 April 1 Introduction This Enhanced Loran eLoran Definition Document has been produced by the International Loran Association to provide a highlevel definition of eLoran for policy makers service providers and users It first describes the eLoran system signal and users receivers It focuses in turn on how eLoran is employed to navigate in the air at sea and on land and then on the use of eLoran in locationbased services as well as a source of highly precise time and frequency This document will be followed by others produced by various bodies including a signal specification and a set of receiver performance standards for the various applications 11 Overview Enhanced Loran is an internationally standardized positioning navigation and timing PNT service for use by many modes of transport and in other applications It is the latest in the long standing and proven series of lowfrequency LOngRAnge Navigation LORAN systems one that takes full advantage of 21st century technology eLoran meets the accuracy availability integrity and continuity performance requirements for aviation nonprecision instrument approaches maritime harbor entrance and approach maneuvers landmobile vehicle navigation and locationbased services and is a precise source of time and frequency for applications such as telecommunications2 eLoran is an independent dissimilar complement to Global Navigation Satellite Systems GNSS It allows GNSS users to retain the safety security and economic benefits of GNSS even when their satellite services are disrupted 12 Background The predecessor of eLoran LoranC delivered a positioning accuracy of 460 meters3 principally to mariners sailing in coastal and oceanic waters When the Global Positioning System GPS appeared in the1980s with its positioning accuracy of tens of meters many began to regard LoranC as irrelevant However others saw it as an essential source of position and time that could still be relied upon if GPS failed In September 2001 almost simultaneously with the 911 act of terrorism the US Government published its Volpe Report4 This spelled out the degree to which the US like other nations worldwide was starting to base its critical infrastructures on GPS The Report explained the vulnerability of GPS and similar GNSS systems to disruption by intentional or unintentional interference It identified Loran as a potential solution to this important problem This attracted interest worldwide and provided an impetus to modernize the Loran system in the US The US Loran evaluation and modernization program5 resulted in this new version of Loran with significantly improved performance It has much better accuracy integrity and continuity while continuing to meet LoranCs traditional availability requirements Table 1 These improvements are realized mainly through the addition of a data channel This data channel allows eLoran to meet the very demanding requirements of landing aircraft using socalled nonprecision instrument approaches and bringing ships safely into harbor in lowvisibility conditions eLoran was also shown to be capable of providing the exceedingly precise time and frequency 2 Lorans Capability to Mitigate the Impact of a GPS Outage on GPS Position Navigation and Time Applications Prepared for the Federal Aviation Administration Vice President for Technical Operations Navigation Services Directorate dated March 2004 3 2005 Federal Radionavigation Systems US Department of Defense US Department of Transportation and US Department of Homeland Security 4 Vulnerability Assessment of the Transportation Infrastructure relying on the Global Positioning System John A Volpe National Transportation Systems Center Final Report August 2001 5 A program directed by the US Congress through the budget appropriation process which began in 1997 and has continued through the current fiscal year totaling 160 M to date Date 12 January 2007 Page 7 of 17 Version 01 eLoran Definition Document For Consultation Comments to ILA by 1 April references needed by the telecommunications systems that carry voice and internet communications Accuracy Availability Integrity Continuity 0004 001 nautical mile 8 20 meters 0999 09999 0999999 1 x 107 0999 09999 over 150 seconds Notes 1 Accuracy to meet maritime harbor entrance and approach 2 Availability integrity and continuity to meet aviation nonprecision approach in the US 3 eLoran meets ITU requirements in G811 for primary reference clocks6 Table 1 eLoran System Performance Requirements One of the data channel messages is used to provide realtime differential corrections These corrections are provided via reference stations that detect tiny variations in the eLoran signal similar to the differential GNSS reference stations allowing receivers to correct for these variations as well as providing information regarding signal integrity eLoran has the potential to back up GNSS taking over seamlessly if the satellite signals are lost thus allowing users to continue to operate and keeping communications and surveillance systems running As eLoran uses highpowered transmitters and lowfrequency signals not microwatts and microwaves like GNSS it is very unlikely to be interfered with or jammed by the same causes that would disrupt GNSS signals This means that small lowcost eLoran receivers even built into GNSS units can mitigate the impact of disruptions to GNSS Moreover eLoran can do things GNSS cannot such as acting as a static compass At sea a new concept of navigation enhanced navigation eNavigation is being developed which requires an exceptionally reliable input of position navigation and time data Uniquely the combination of GNSS and eLoran has the potential to meet its needs eLoran is the culmination of technical developments undertaken worldwide over the past two decades which now meets the very demanding requirements of 21st century users 13 Contents In this document Section 2 will introduce the eLoran system and its signal the transmitting stations the monitoring and control arrangements and the user equipment In Section 3 the use of eLoran in aviation maritime land mobile and locationbased services and time and frequency applications will be illustrated as well as the safety security and economic benefits offered by eLoran within each of these applications Section 4 will discuss the eLoran Service Provision as well as the technical documentation that is needed to fully define the performance of the eLoran system 2 The eLoran System eLoran meets a set of worldwide standards and will run wholly independently of GPS GLONASS Galileo or any future GNSS Each users eLoran receiver will be operable in all regions where eLoran service is provided eLoran receivers shall work automatically with minimal user input The foundation for the eLoran signal is the US Coast Guard Specification of the Transmitted LoranC Signal7 However for eLoran use many of the tolerances have been tightened in order to ensure that eLoran meets the new much higher standards Details of these changes will be 6 Timing Characteristics of Primary Reference Clocks International Telecommunications Union G811 September 1997 7 Specification of the Transmitted LORANC Signal United States Coast Guard COMDTINST M165624A 1994 Date 12 January 2007 Page 8 of 17 Version 01 eLoran Definition Document For Consultation Comments to ILA by 1 April specified in later documents The change to eLoran will not preclude the continued use of legacy LoranC receivers but legacy users will not benefit from the additional data channel capabilities of eLoran Figure 1 eLoran System Concept Because eLoran signals travel over the surface of the earth ie they are groundwaves they are subject to small propagation delays that depend on the electrical conductivity of the ground To achieve the high level of accuracy required for aviation approaches harbor entrance and approach maneuvers and to recover precise time these propagation delays must be measured and the corrections must be applied User and System Monitor Receivers will store and employ these Signal Propagation Corrections to maximize the accuracy and also provide integrity for the solutions they deliver 21 eLoran Signal The principal difference between the eLoran transmitted signal and the traditional LoranC signal is the addition of a data channel The data channel conveys corrections warnings and signal integrity information to the users receiver via the Loran transmission The data transmitted may not be needed for all applications but will include at a minimum The identity of the station an almanac of Loran transmitting and differential monitor sites Absolute time based on the Coordinated Universal Time UTC scale leapsecond offsets between eLoran system time and UTC Warnings of anomalous radio propagation conditions including early skywaves warnings of signal failures aimed at maximizing the integrity of the system Messages that allow users to authenticate the eLoran transmissions officialuse only messages Differential Loran corrections to maximize accuracy for maritime and timing users and Differential GNSS corrections Date 12 January 2007 Page 9 of 17 Version 01 eLoran Definition Document For Consultation Comments to ILA by 1 April 22 Transmitting Stations All eLoran transmitters use modern solidstate transmitter SSX and control technology They have uninterruptible power supplies UPS that ensure that any failure of the incoming power will neither interrupt nor affect the transmitted signal The time and frequency control systems of the transmitter are designed for eLoran operation and they apply phase corrections in a continuous manner The time reference system uses multiple cesium clocks or an alternative technology of at least equal quality eLoran transmissions are synchronized to an identifiable publiclycertified source of Coordinated Universal Time UTC by a method wholly independent of GNSS This allows the eLoran Service Provider to operate on a time scale that is synchronized with but operates independently of GNSS time scales Synchronizing to a common time source will also allow receivers to employ a mixture of eLoran and satellite signals When an eLoran station is detected as being out of tolerance it is immediately taken off the air to ensure that receivers promptly cease to use its signals Traditional LoranC blinking8 is used to show that a station is under test and should not be used 23 Control Centers eLoran transmitting stations run unattended Sufficient personnel are at the control centers and on call to respond rapidly to failures and to maintain the published very high levels of availability and continuity Scheduled maintenance work is planned carefully to minimize the impact on users of stations being off the air Users are given adequate notice of interruptions via well publicized channels of communication Security of these sites and of any critical communications systems is of a high level reflecting the importance of the applications for which the transmitted signal is being used 24 Monitor SitesReference Stations Monitor sites located in the eLoran coverage area are used to provide integrity for the user community The receivers used at these sites monitor the eLoran signals and provide realtime information to the control centers regarding signals in space Users are notified immediately if any abnormalities are detected Some of the monitor sites will be used as reference stations to generate the data channel messages Selected sites will also have at least one highly accurate clock for synchronization to UTC to provide time and frequency corrections for timing users A monitoring network will be established to provide realtime maritime differential corrections and provide warnings for aviation users 25 Users Equipment eLoran users receivers operate in an allinview mode That is they acquire and track the signals of many Loran stations the same way GNSS receivers acquire and track multiple satellites and employ them to make the most accurate and reliable position and timing measurements Another benefit of using the allinview mode is that it ensures that the eLoran receiver is always tracking the correct cycle of each individual signal An eLoran receiver is capable of receiving and decoding the data channel messages and applying this information based on the user specific application Figure 2 This information coupled with the published Signal Propagation Corrections provides the user with a highly accurate PNT solution 8 Specification of the Transmitted LORANC Signal United States Coast Guard COMDTINST M165624A 1994 Date 12 January 2007 Page 10 of 17 Version 01 eLoran Definition Document For Consultation Comments to ILA by 1 April Figure 2 Data Channel Messages 3 Applications 31 Overview Minimum Operational Performance Standards MOPS will be published to set the standards for receiver performance based on the user application 32 Aviation Aviation navigation services support aircraft operations in the departure enroute and approach and landing phases of flight In the US LoranC has long been approved by the Federal Aviation Administration FAA for use by aircraft with certified receivers for flying enroute and making departures and arrivals but not for the critical approach and landing phases The much higher accuracy availability integrity and continuity of eLoran does meet the specifications for each of these phases allowing eLoran to support aircraft operations from gatetogate eLoran meets the requirement for socalled nonprecision approaches this means that although eLoran which has no means of measuring height will not provide any vertical guidance it will provide sufficient horizontal guidance Specifically eLoran has been shown to meet the Required Navigation Performance 03 RNP 03 aviation specification which has the following stringent requirements Horizontal Accuracy Availability Integrity Continuity 03 Nautical Mile 556 meters 0999 09999 1 x 107 per hour 0999 09999 Table 2 Requirements for RNP 03 The term RNP 03 refers to the accuracy specification of 03 nautical miles 556 meters Because this tolerance must also accommodate deviations resulting from human factors eLoran must provide a more stringent horizontal position accuracy of 307 meters 95 of the time To ensure that eLoran meets these requirements the Signal Propagation Corrections are published for each airport and applied by the user receiver in realtime during each phase of operation The key to meeting the high availability requirement is the eLoran receivers use of allinview technology The performance of the system must also be maintained throughout each approach Date 12 January 2007 Page 11 of 17 Version 01 eLoran Definition Document For Consultation Comments to ILA by 1 April with its duration of some 150 seconds The allinview receiver technology ensures that eLoran does so with the required probability of 999 9999 The most demanding part of the specification and the key to maintaining the safety of an aircraft instrument approach is the integrity requirement of 1 x 107 This means that the probability of the receivers producing position information that is hazardously misleading must be shown to be less than 1 in 10000000 per hour Extensive analyses have demonstrated that the eLoran system can achieve this most stringent requirement Most eLoran aviation receivers employ socalled Hfield or magnetic loop antennas Extensive tests have shown that these antennas are almost immune to the effects of the Precipitation Static PStatic experienced in rain and snow which has been a major problem for users of traditional LoranC airborne receivers Benefit Description Safety Maintains the gatetogate area navigation RNAV operational concept and benefits when GNSS is disrupted Security Maintains airtoground and airtoair situational awareness using ADSB when GNSS is disrupted Economic Has the potential to reduce ground based infrastructure and avoid the cost of recapitalizing Allows the continued use of the dispatch and economic routing structure Enables Communications Navigation and Surveillance CNS functions to migrate to digital communications Table 3 Summary of eLoran aviation benefits 33 Maritime The worlds shipping industry is experiencing strong growth which is expected to continue Ships are getting larger and faster sealanes are becoming more crowded and crews are increasingly relying on electronic navigation systems to operate in this environment9 The newly proposed concept of eNavigation will improve safety security and protection of the marine environment as well as potentially reducing costs It will provide bridge officers with all the information they need on a single display In order to make these critical enavigation services available the system will require a supply of position and timing data of exceptionally high accuracy and reliability This information will come principally from GNSS But GNSS alone cannot be guaranteed to meet the availability and reliability required Uniquely the combination of GNSS and eLoran will do so with the two systems operating independently of one another but providing a single combined output data stream Thus eLoran is the key that will enable eNavigation to deliver its full range of benefits and maintain safety through redundancy10 The high availability achieved could also lead to a reduction in the number of traditional physical aids to navigation lights and buoys with potentially substantial cost savings The International Maritime Organization IMO sets the navigation performance requirements for systems to gain acceptance into the World Wide Radionavigation System WWRNS These apply in harbor entrances harbor approaches and those coastal waters with a high volume of traffic andor a significant degree of risk11 9 2020 The Vision General Lighthouse Authorities of the United Kingdom and Ireland October 2004 10 The Case for eLoran General Lighthouse Authorities of the United Kingdom and Ireland May 2006 11 WorldWide Radionavigation System International Maritime Organisation Resolution A95323 December 2003 Date 12 January 2007 Page 12 of 17 Version 01 eLoran Definition Document For Consultation Comments to ILA by 1 April Accuracy Signal Availability Time to Alarm Service Reliability 10 meters 95 0998 over 2 years 10 seconds 09997 over 3 hours Table 4 IMO requirements for harbor or coastal operations A number of demonstration projects and studies in the US and Europe have shown that eLoran can meet these requirements12 The most demanding specification is the accuracy of 10 meters 95 Achieving this requires two key components The signal propagation errors along the channels and throughout the harbors must be measured The resulting Signal Propagation Corrections are published and stored in each receiver Realtime differential Loran corrections are applied to remove the small fluctuations in the signals due to weather or transmitter timing variations By using these realtime corrections ships achieve the exceptional accuracy required for safe navigation in confined waterways eLoran supplies the precise timing needed to support not only eNavigation but also the Automatic Identification System AIS and synchronized lights in harbor areas The performance requirement that eLoran must meet for these timing applications is the International Telecommunication Unions ITU standard ITU G81113 This specifies the relative phase stability required of primary reference clocks 1 1011 An important bonus of using eLoran something GNSS cannot provide is the eLoran compass When the receiver is used with an Hfield Magnetic Loop antenna it can be employed as an automatic directionfinder taking bearings on the transmitting stations From these the receiver calculates the ships heading generally with an accuracy of better than 1 and independent of the ships movement eLoran maritime equipment will be required to meet minimum operational performance standards MOPS that will be issued in due course by the IMO the International Electrotechnical Commission IEC or eLoran service providers These documents will also specify the interfaces of the eLoran receiver with shipborne navigation equipment such as the Electronic Chart Display and Information System ECDIS or AIS Benefit Description Safety Maintains eNavigation operations when GNSS is disrupted rather than the ship reverting to traditional operations using physical aids to navigation AtoN Enables permanent or temporary virtual AtoNs to be used to mark dangerous waters In conjunction with a robust collision warning systems this will enhance the safety of life at sea Security Supports robust collision warning systems during GNSS disruptions Maintains Vessel Traffic Service situational awareness using the marine Automatic Identification System when GNSS is disrupted Economic Potentially reduces the number of collisions and groundings leading to a reduction in oil spills and assists with pollution monitoring Potentially decreases the total cost of AtoN service provision Potentially improves onboard operational efficiency including routing and access to ports 12 The General Lighthouse Authorities Loran Programme and Current Status in Europe Basker S Proc International Loran Association 2006 Convention and Technical Symposium Groton CT October 2006 13 Timing Characteristics of Primary Reference Clocks International Telecommunications Union G811 September 1997 Date 12 January 2007 Page 13 of 17 Version 01 eLoran Definition Document For Consultation Comments to ILA by 1 April Table 5 Summary of eLoran maritime benefits 34 Land Mobile eLoran will provide PNT data for a variety of land mobile applications working alongside GNSS However it can also provide the eLoran compass capability to determine the heading of a vehicle even when it is stationary eLoran via the data channel can authenticate its own and GNSS data when it is used for toll collection or vehicle monitoring It is perhaps on land that eLorans greatly enhanced immunity to jamming compared to that of GNSS will prove to be of the greatest value eLoran employs highpowered transmitters so the signals reaching receivers are of much greater strength than those of GNSS and require much more power to jam Given that radiating significant power efficiently at the low frequency and long wavelength of Loran requires large antenna structures it is extremely difficult to produce a signal that could jam an eLoran signal over more than a very small local area In contrast jamming a GNSS signal even over a whole city for example to block a road pricing system is not very technically demanding A further important benefit of eLorans low frequency signals is their ability to penetrate into places where GNSS signals either cannot be received at all or where they are intermittent or inaccurate These include the urban canyons in the centers of major cities Loran signals have been shown to penetrate reliably into steel shipping containers refrigerated vehicles and storage warehouses14 This ability has led to the development of systems that track items either of high value or whose safe and timely delivery must be guaranteed The tracking of hazardous cargoes also demands the consistent updates and high availability of eLoranbased systems Unlike aviation and maritime systems those designed for land tracking applications are generally not required to meet published performance standards Rather their performance is normally assessed and optimized for user specific applications Benefit Description Safety Provides effective and timely emergency response and routing in response to an E911 or E112 report Permits positive vehicle control Security Enables tracking of hazardous cargo highvalue assets and other vehicles of interest when GNSS is disrupted or cannot be received Assists in vehicle theft prevention and recovery Economic Allows for traffic characterization using the Floating Car technique to assist fleet tracking management and routing Supports road user charging providing authentication Table 6 Summary of eLoran landmobile benefits 35 LocationBased Services eLoran services will also deliver PNT data to support numerous location based services ie personal applications eLorans ability to penetrate into urban canyons and building can assist service providers in meeting the evolving PNT performance requirements including those for E 911US or E112 Europe response systems Other applications include but are not limited to locationbased encryption systems geofencing weather balloon tracking offender tracking and locationbased billing 14 Test results of the eTracker a new modular and flexible LoranC based goods tracking system Clerens M Proc International Loran Association 2006 Convention and Technical Symposium Groton CT October 2006 Date 12 January 2007 Page 14 of 17 Version 01 eLoran Definition Document For Consultation Comments to ILA by 1 April The performance standards for these applications as with those for any land mobile applications need to be assessed and optimized for user specific applications Benefit Description Safety Tracks people including children Provides lone worker protection Assists E911 or E112 reporting Security Provides geofencing for offender tracking Allows locationbased encryption Economic Tracks weather balloons Weather forecasting Locationbased marketing and billing Table 7 eLoran locationbased service benefits 36 Time Frequency Using GNSS is now the principal method of recovering UTC time worldwide GNSS is extensively employed as a time source in the telecommunications and many other industries It provides time with an accuracy of 5 100 nanoseconds eLoran is a viable alternative source of time since its transmissions are precisely synchronized to UTC The data channel carries messages that receivers use to identify the timing of each individual eLoran pulse from each station Other messages on this channel also correct for small variations caused by propagation delays Employing them allows absolute UTC time to be recovered with an accuracy of 50 nanoseconds Thus an eLoran timing receiver can serve as a reference clock a primary source of time or as an alternative to GNSS combined GNSSLoran timing receivers are available commercially A particular advantage of eLoran over GNSS is the availability of its signals indoors This avoids the need to install an outside antenna with a clear view of the sky something that can be particularly difficult and even expensive in downtown citycenter locations and highrise buildings eLoran is also used as a source of precise frequency frequency is the rate of change of a clock eLoran timing receivers have been shown to meet the Stratum 1 1x1011 frequency standard even without differential corrections And this can be done with an indoor antenna Benefit Description Safety Ensures continuity of telecommunications network for E911 or E112 Security Maintains power grid phase synchronization flow control and fault isolation Provides the timing source for encrypted communications Economic Maintains synchronization of wired and wireless telecommunications without the need for expensive external oscillators Timestamps banking and share trading transactions Synchronizes digital television Table 8 Summary of eLoran time and frequency benefits 4 eLoran Service Provision eLoran services will deliver benefits to a wide range of stakeholders eg governments service providers and users eg aviation maritime From a service provision perspective eLoran may be considered as comprising Date 12 January 2007 Page 15 of 17 Version 01 eLoran Definition Document For Consultation Comments to ILA by 1 April Core eLoran Service Provider delivering a highly precise version of the core signal originally described in the US Coast Guard Specification of the Transmitted LoranC Signal and Figure 3 eLoran service provision Application Service Providers eg aviation maritime etc delivering applicationspecific data eg differential Loran messages or early skywave warnings that may be communicated using a data channel on the eLoran signal Transmitting Stations Differential Loran Ref Station Monitoring Sites Control Center Maritime Service Provision Core eLoran Service Provision Diff Loran Corrections Diff Loran Corrections Diff Loran Corrections eLoran Signal eLoran Signal eLoran Integrity eLoran Integrity eLoran Integrity eLoran Signal The Maritime Service Provider is responsible for generating the Diff Loran Corrections and providing Signal Propagation Maps Figure 4 Example of an eLoran service provision for maritime users Date 12 January 2007 Page 16 of 17 Version 01 eLoran Definition Document For Consultation Comments to ILA by 1 April 41 Documentation Three documents are required to define fully an eLoran service Table 9 a plan a performance specification and an interface control document The eLoran plan and performance specification will be owned by the service provider The eLoran interface control document shall be standardized globally to ensure interoperability Document Description Plan Addresses policy considers operational issues presents a service description and identifies future developments It may include a summary of user requirements that are met Example US Federal Radionavigation Plan15 Performance Specification Defines the level of performance including coverage that the service provider is committed to providing It may take the form of a service level agreement Example US GPS SPS Specification16 Interface Control Document Defines the signal so that it can be accessed by user equipment Example GPS ICDGPS 20017 Table 9 eLoran service definition documentation Each Core eLoran Service Provider and each Application Service Provider will need to develop its own service definition documents based on international standards and local service provision requirements 5 Conclusion eLoran as an internationally standardized positioning navigation and timing PNT service will be available for a wide range of applications and is an independent dissimilar complement to Global Navigation Satellite Systems GNSS PNT users will be capable of retaining the safety security and economic benefits of GNSS even when their satellite services are disrupted or when using eLoran in areas where GNSS in not available eLoran is capable of providing this level of service by meeting the accuracy availability integrity and continuity performance requirements for aviation nonprecision instrument approaches maritime harbor entrance and approach maneuvers landmobile vehicle navigation locationbased services precise time and frequency users This document the first of several needed to fully define the system marks the beginning of an international effort to secure accurate and reliable sources of PNT for 21st century users with demanding safetycritical or missioncritical applications 15 2005 Radionavigation Plan Published by US Department of Defense Department of Homeland Security and Department of Transportation January 2006 16 Global Positioning System Standard Positioning Service Performance Specification US Department of Defense October 2001 17 NAVSTAR GPS Space Segment Navigation User Interfaces ARINC Research Corporation ICDGPS200 Rev C October 1993 Date 12 January 2007 Page 17 of 17 Version 01