European Maritime Radionavigation Forum
Briefing Notes for EMRF Meeting on 29 September 2016
1.ERNP: EC developments; outline for maritime section of ERNP
Two attempts have been made in the past to provide a European Radio Navigation Plan. Although these plans were completed, they were never published or adopted. There have been some signs of renewed interested from the European Commission in the last two years. The EMRF may wish to consider contributing a discussion paper on the maritime aspects and proposing that the plan is broadened to include Timing.
2.GNSS
GPS is in a stable state with 31 operational satellites, providing an excellent PNT service, although there are ongoing concerns about funding and the replacement ground control system, in particular. GLONASS has 24 operational satellites providing global coverage and the replenishment program is continuing. Galileo currently has 8 satellites available with two more under commissioning and four more scheduled for launching later this year. Services are planned to start, with timing applicationsin October. Six new-generation BeiDou satellites are in orbit, with an eventual constellation of five geostationary (GEO) satellites, three inclined geostationary orbit (IGSO) satellites, and 27 middle-Earth-orbiting (MEO) satellites planned for the global system expected to be in place by 2020. India successfully launched the seventh and final spacecraft for the Indian Regional Navigation Satellite System, now renamed NAVIC. This is an independent regional navigation satellite system designed to provide position information in the Indian region and 1,500 km around the Indian mainland.
3.Augmentation Systems:
a.GBAS
Ground Based Augmentation Systems consist of reference stations and integrity monitors, which receive the GNSS signals and generate correction data and integrity messages for broadcast to the user receiver. A ‘virtual’ reference station network may be formed, computing corrections for any point within the coverage area. The IALA DGPS system uses MF beacons to broadcast the data and is in operation in most parts of the World. It is the accepted maritime augmentation system, although the US has announced plans to shut down a large number of its inland stations.
b.SBAS
Satellite Based Augmentation Systems (SBAS) are correction and integrity monitoring systems consisting of a network of ground reference stations, data centres and uplink sites, used in conjunction with geo-stationary satellites which broadcast correction data to the user receiver, usually in the L Band used for the primary GNSS service. WAAS (N America), EGNOS (Europe), GAGAN (India) and MSAS (Japan) have approval and certified receivers for aviation applications. The Beidou augmentation element using GEOs will start deployment in 2018 and the Russian system SDCM is expected to become operational soon.
The providers of EGNOS are making considerable efforts to broaden its use beyond aviation, including into the maritime sector. SBAS providers in other parts of the World do not appear to be concerned with maritime applications, although many marine receivers, particularly in the leisure market are SBAS enabled. Many mariners are using SBAS without being aware of it and there are currently no established receiver standards or procedures for providing status information or warnings to the mariner.
4.Resilient PNT:
a.Report on Resilient PNT Forum
The fifth Resilient PNT Forum was held in Helsinki on 30 May, immediately before ENC-2016. With a keynote presentation from Prof. David Last, there was a good attendance and lively discussion. There was a general consensus that another event should be held, with an emphasis on timing applications, therefore the sixth RPNT Forum is planned for 7 November in association with the RIN International Navigation Conference in Glasgow.
b.Update on potential backups: eLoran; R-mode; Radar Positioning; Other
eLoran
Initial Operational Capability (IOC) of eLoran was established for seven major ports on the East coast of the UK in 2014. This gave positioning accuracies of 10 m (95%) in the ports and their approaches, with accuracies in the region of 50 m along the coasts. This meets the harbour/harbour approach requirements set out in IMO Resolution A.1046(27) for a World Wide Radio Navigation System and the proposed requirement for a backup system in coastal waters. However, termination of transmissions from the stations in France, Norway and the Faeroes at the end of 2015 meant that there was no longer a navigation service in NW Europe. Meanwhile the US appears to be moving towards reversing its decision to close down Loran transmissions, in order to provide a backup to GPS, initially for timing, but eventually for positioning too. A commercial consortium is proposing to take over operation of the stations there and is in negotiation to do the same in Europe.
Loran systems also exist in other parts of the world, notably the People’s Republic of China, the Republic of Korea, Russia (Chayka), India and Saudi Arabia. Proposals to modernise these systems to provide eLoran are at different stages of development.
R-mode
Ranging mode has been demonstrated on an MF beacon in the Netherlands and test results are promising. However, considerable work is still needed on technical development, frequency and coverage planning and regulatory arrangements. The advantages of this option would be its world-wide applicability, although coverage would depend on station availability and geometry. Ranging on AIS transmissions has also been demonstrated to show that accuracies in the order of 10m (95%) can be achieved (with good geometry and timing corrections). Given a suitable multi-system receiver, ranging signals from different sources could be combined, together with those from Loran, to provide a much more widespread service.
Radar positioning
Trials carried out in the EfficienSea and ACCSEAS projects demonstrated that good accuracies could be provided using range and bearing from a specially designed, digital radar, in conjunction with enhanced radar beacons on shore. The racon signals were modulated with information on their identity and/or location to allow the processing in the radar to produce a fix. Usable ranges were limited to about 10 M from the coast and the number of enhanced racons required would be large. However, the major obstacle would be the need to replace or modify all the existing radars on ships, making this a difficult and very long-term solution. However, another approach being explored is the use of ‘map matching’ using added processing in the radar to recognise the coastline and provide a position from the map developed. This could be an automatic ‘learning’ process, using other sensors as references. There is considerable technical development work required and there would still need to be some modification or added equipment to existing radars.
Non-radionavigation options
Inertial systems, using gyroscopes and accelerometers, have advanced in recent years, but mainly at the lower end of the market, with micro-electromechanical systems (MEMS) devices providing low-cost sensors for land vehicle and personal navigation. At the higher end, navigation grade inertial devices remain expensive and still do not have the long-term stability needed for a full back-up to GNSS. Some experts believe that there are fundamental barriers to such an application, but in any case it appears to be some way in the future. Another solution for the future could be quantum devices, tracking the perturbation of atoms using lasers, on which considerable research effort is being expended.
The use of visual marks is another non-radio possibility and a working prototype of a relatively low-cost ePelorus has been produced and demonstrated. This makes use of existing visual aids to navigation and other landmarks, in conjunction with an electronic chart to establish the user’s position, using a self-contained,on-board device. It is of course limited by visibility and the availability of suitable marks.
c.Resilient PNT Guidelines
Work continues in the IMO Correspondence Group, led by Germany. Comments have been provided by CIRM, Finland and the UK and an input is expected to be available for consideration at NCSR 4 in 2017.
d.Multi-system receiver
The RPNT Guidelines will support the new performance standard agreed in IMO for a multi-system receiver. This will use whatever positioning signals are available – multi GNSS, or terrestrial to arrive at the best position, carrying out integrity checks to ensure that erroneous information does not degrade the solution. Receivers designed to this standard are expected to become available from 2019.