The Japanese government has ordered three navigation satellites from Mitsubishi Electric Corp. to expand the Quasi-Zenith Satellite System (QZSS), reports Spaceflight Now. QZSS augments GPS navigation signals for users in the Asia-Pacific region.
NEC Corporation has also been awarded a contract, for the Ground Control Segment.
Japan’s Cabinet Office announced the QZSS expansion on March 29, approving a $526 million contract with Mitsubishi Electric for the construction of three satellites for launch before the end of 2017. Two of the spacecraft will be placed in inclined orbits, and one satellite will operate in geostationary orbit over the equator.
Michibiki, the website version.
NEC Corp. will operate QZSS for 15 years under a $1.2 billion contract that covers the design, verification and maintenance of the QZSS ground system.
The International GNSS Service (IGS), a worldwide federation of agencies involved in high-precision Global Navigation Satellite System applications, has announced the launch of its Real-Time Service (RTS). The RTS is a global-scale GNSS orbit and clock correction service that enables real‐time precise point positioning (PPP) and related applications requiring access to IGS low latency products.
The RTS is offered in beta as a GPS-only service for the development and testing of applications. The Russian GLONASS is initially provided as an experimental product and will be included within the service before the end of 2013 as the RTS reaches its full operating capability. Other GNSS constellations will be added as they become available.
The RTS is operated as a public service. Users are offered free access through subscription. Interested parties are invited to visit the service’s website.
The IGS is a worldwide federation of more than 200 organizations that operate a cooperative global infrastructure to provide the highest-quality GNSS data products for scientific users. The IGS is a service of the International Association of Geodesy (IAG), one of the associations of the International Union of Geodesy and Geophysics (IUGG). It is also a service of the World Data System of the International Council for Science (ICSU/WDS).
Scientists in Hanoi, Vietnam, send word that on March 27 the four Galileo in-orbit validation satellites were visible at the same time in the sky over that Southeast Asian country for nearly two hours (from 2:15 to 4:00 GMT) while transmitting a valid navigation message.The research team of the NAVIS Centre at Hanoi University of Science and Technology (HUST) successfully computed what they claim is the first Galileo-only position fix in Asia.
Figure 1 depicts the obtained positions are depicted on top of the roof of the NAVIS Centre, where the antenna used to receive the signals is located (latitude = 21°00’16.69” N, Longitude = 105°50’37.90” E, height = 35,2 meters).
Figure 1. Positions obtained by only Galileo E1 Open Service (the antenna is located at the roof of the Ta Quang Buu library building inside HUST campus)
Figure 2 shows the positions of the four Galileo satellites and of 12 GPS satellites at time of acquisition, while Figure 3 reports the acquisition results of the four Galileo IOV satellites.
Figure 2. Skyplot of the satellites of the GPS and Galileo systems at the time of the campaign. The Galileo satellites are PFM (PRN11), FM2 (PRN12), FM3 (PRN19), and FM4 (PRN20).Figure 3. Acquisition results of the four Galileo IOV satellites: PRN 11.Figure 3. Acquisition results of the four Galileo IOV satellites: PRN12.Figure 3. Acquisition results of the four Galileo IOV satellites: PRN19.Figure 3. Acquisition results of the four Galileo IOV satellites: PRN20.
Comparison of the position computed using only Galileo, only GPS or both systems together is also presented in Figure 4. It should be noted that during the campaign, the data demodulation process reports that the Galileo system announces the “navigation data valid” status for PFM and FM3, meanwhile the “working without guarantee” for FM2 and FM4.
Figure 4. Position computed when using GPS only, Galileo only, or GPS+Galileo
The NAVIS Centre, located at the Hanoi University of Science and Technology in Hanoi, Vietnam, was established with a project co-funded by the European Union and collaborates with European and Asian partners on research and development of satellite navigation technology in Southeast Asia. This report was made by Dr. Ta Hai Tung, director of the NAVIS Centre, and Prof. Gustavo Belforte, co-director.
eLORAN Initial Operational Capability at the Port of Dover
An overview of the work of the General Lighthouse Authorities of the United Kingdom and Ireland on the implementation of Enhanced Loran Initial Operational Capability (IOC) in the waters around Great Britain. eLoran is the latest in the longstanding and proven series of low-frequency, LOng-RAnge Navigation systems. It evolved from Loran-C in response to the 2001 Volpe Report on GPS vulnerability. It vastly improves upon previous Loran systems with updated equipment, signals, and operating procedures.
By Paul Williams and Chris Hargreaves
GPS/GNSS is everywhere! It is used in many ship’s systems (Figure 1), but it is vulnerable to interference both intentional and unintentional.
Its output is displayed on the electronic chart display and information system; is transmitted to other vessels using the Automatic Identification System (AIS); is used to calibrate the gyro compass; is used in the radar; is connected to the digital selective calling, its reported position transmitted at the push of the emergency button for search-and-rescue; is in the vessel data recorder, the dynamic positioning system, surveying equipment, the ship’s entertainment system for aiming the satellite dish; and it even synchronizes the ship’s clocks!
28 days worth of ship-traffic data for the Strait of Dover.
GNSS is also used in marine Aids-to-Navigation (AtoN) provision, for deploying buoys and lights, AIS transponders, and AtoN position monitoring, and its precise timing capabilities are used to synchronise the lights along an approach channel to improve conspicuity.
GNSS (effectively GPS) has become the primary Aid-to-Navigation (AtoN) used by all professional and most other mariners. The vulnerability of GNSS to space weather and interference (unintentional and criminal jamming) means that a backup system is needed to achieve resilient Position, Navigation, and Timing (PNT) for e-Navigation. Though the probability of losing GNSS may be low, the consequential impact could be very high, and maintaining an appropriate balance of physical and radionavigation AtoNs is vital for e-Navigation.
Figure 1. GPS is used in many ship’s systems.
The International Maritime Organisation seeks to develop a strategic vision for e-Navigation, integrating existing and new navigational tools in an all-embracing system, contributing to enhanced navigational safety and environmental protection, while reducing the burden on the navigator. One of IMO’s requirements for e-Navigation is that it should be resilient — robust, reliable and dependable.
The General Lighthouse Authorities of the United Kingdom and Ireland (GLAs) have the statutory responsibility to provide marine AtoNs around the coast of England, Wales, Ireland, and Scotland. It has become clear over recent years that if the GLA chose to implement eLoran, it could rationalize its physical AtoN infrastructure, removing some lights and other physical aids, and on balance actually reduce costs by implementing eLoran. Indeed, compared to other possible resilient PNT options such as GNSS hardening, radar absolute positioning, increasing physical AtoN provision, eLoran would save the GLAs £25.6M over a nominal system lifespan of 10 years from the introduction of e-Navigation services in 2018 to 2028.
Not So Old-Fashioned. How does the new eLoran differ from the old, outdated, Loran-C system? The core signal of eLoran is pretty much the same as Loran-C, but tolerances have been tightened up. Things like carrier zero crossing points, half-cycle peaks, ECDs, transmission timing, signal power, signal availability, power supply resilience have all been upgraded, taking advantage of improvements in technology allowing us to better appease the so-called four horsemen of navigation: accuracy, availability, continuity, and integrity.
SAM control is a thing of the past, and eLoran transmitters are synchronised directly to UTC. This means that their times of transmission can be predicted. Having stations independently synchronised to UTC means that the mariner no longer has to rely on old-fashioned hyperbolic navigation. Charts with hyperbolic lines of position on them are also a thing of the past. A modern eLoran receiver works just like a GPS receiver, employing signals from all available transmitters in its position solution. With GPS those transmitters are moving in space; in eLoran the transmitters are fixed onto the surface of the Earth.
Reelektronika LORADD receiver, only 3 centimeters tall.
Modern receivers are small (photo). They use off-the-shelf, high-performance processors, and the receiver is written in software, allowing a lot of flexibility.
Three transmitters are sufficient to give you position; four or preferably five signals are better for integrity. But for timing and frequency applications you only need one transmitter. The Anthorn station in the UK can cover the entire UK and Ireland with a radio signal that has stability enough to satisfy the Stratum 1 frequency source requirement for steering the clocks of telecom networks, and Anthorn has not even been upgraded to full eLoran standard yet!
One of the big differences between Loran-C and eLoran is that eLoran now has a data channel. Some of the Loran pulses of each pulse group are modulated so that data can be sent over the 100kHz signal. This allows service providers to send integrity alerts, and application-specific data, like UTC time, and differential-Loran (DLoran) and DGPS corrections. In Europe this is implemented by the already internationally standardised Eurofix system.
A parallel can be drawn with GPS signals, which contain a navigation component (pseudorandom noise code and/or carrier phase) and modulated data. Some options for data channel technology are still evolving with 1500 bits per second demonstrated, and 3000 bps possible. That may not sound very much to salt-of-the-earth communications engineers, but for Loran it’s pretty impressive, especially when you consider prototype attempts at Loran data communications in the past have been limited to 30 to 250 bps.
Maritime Applications Services
How do we apply eLoran to something like the maritime application of port approach? It is important to remember that the receiver operates by measuring how long it takes a groundwave radio signal to travel over the surface of the earth. An eLoran receiver assumes that the world is made entirely of seawater, for which it has a very accurate propagation model built in. The receiver does not, and indeed cannot, know about any land along the propagation path; and land slows the signal down, perhaps by as much as a few microseconds, over typical propagation distances.
So the service provider must survey the effects of the land masses in the area of coverage. The Additional Secondary Factors (ASFs) of all the stations across the proposed service area are therefore mapped. The ASF survey is a once-and-for-all task, but it needs to be done and the ASFs published. In the old days, hyperbolic lines would be “grid warped,” or tables would be published on paper for the navigator to enter values manually. But with modern eLoran receivers containing large amounts of memory, quite detailed ASF maps can be stored in the mariner’s receiver.
ASFs depend on the electrical conductivity of the surface over which the eLoran signal travels. The conductivity changes with the constitution and moisture content of the earth. This means that the ASF along a path varies over a period of time —perhaps by as much as a few hundred nanoseconds over a year. Because the ASFs in a receiver are fixed, a method is needed to correct for this temporal ASF variation. In order to monitor this variation, a reference station is installed close to the harbor or point of use of the eLoran service. This DLoran reference station measures the temporal changes in the signals’ arrival times due to changing ASFs, transmitter variations, and weather effects.
The phrase “reference station” conjures up images of expensive buildings, amenities, and hordes of personnel and associated support services. However, a DLoran reference station is a small box sitting in the corner of a room connected to a small eLoran receive antenna on the roof, and to the Internet. It sends differential corrections over the Internet to an eLoran transmitter, which then broadcasts them to the mariner’s receiver over the Loran Data Channel, for example Eurofix.
Note that a DLoran reference station does not transmit a radio signal. It does not need a transmitter itself; it uses the Internet and the eLoran signal to disseminate its real time data. The mariner uses the same eLoran receiver to receive both the navigation signal AND the differential corrections.
So the process is: map ASFs once; run a reference station; and broadcast corrections. That’s it! With good signal-to-noise ratio and transmitter geometry, 10-meter or better accuracy can be obtained.
Measuring ASFs
The GLA have had the ability to measure ASFs for several years, using a combination of commercial hardware and proprietary software (Figure 2).
Figure 2. GLA-produced software for ASF survey, processing, and validation.
The software, written in Matlab, shows a real-time plot of the survey as it progresses. The ASF values are color-coded according to magnitude. The software can also process the ASF data once it has been measured, to get the best performance out of it. The real-time capabilities of the software allow the determination of the quality of the data while aboard the ship, rather than having to wait until back in the laboratory. Statistical analysis of the data can also show where the ship should go to gather more data in a particular area.
Once the survey is complete, the software can be used to generate interpolated grids of ASF data — the most convenient and accurate form of ASF data storage.
It is important with any scientific or engineering measurement to establish the error on that measurement. The same can be said of ASFs, and so the software can calculate the error bounds on ASF measurements. This “ASF error” data can again be published in grid form alongside the ASF database. This allows it to be used as one component of an Integrity Equation, implemented within the mariner’s receiver, to calculate Horizontal Protection Level (HPL).
After processing, the ASF data should be validated by performing a harbor approach or other maneuver that requires a particular positioning accuracy. For this, the software can be switched to “Validation” mode. Once the validation is successful, the data can be output in a publication format (RTCM SC-127 format for example).
The plot in Figure 2 shows part of an ASF database for Harwich and Felixstowe, major ports on the east coast of the UK. Using this data and DLoran in the Harwich and Felixstowe approach provides 10-meter (95 percent) positioning accuracy.
UK eLoran Prototype
This prototype eLoran system works alongside GPS. It has been in operation 24 hours a day since May 2010. It is “prototype” because it demonstrates the concept of eLoran using signals from existing Loran-C stations in Norway, the Faroe Islands, Germany, and France plus the UK’s station at Anthorn; see Figure 3.
Figure 3. Relevant European Loran-C stations for prototype eLoran.
These stations, together with ASF measurements and DLoran, can deliver a high-precision eLoran service in ports where 10-20 meter accuracy is needed, across the area enclosed by the green contour in Figure 4.
Figure 4. Coverage of prototype eLoran over the UK and Ireland.
It is very impressive, yet the full availability and accuracy benefits of eLoran are still to come as these stations are eventually upgraded to full eLoran capability. And for the last year or so, the GLA have begun to move beyond the confines of the Harwich and Felixstowe approaches and implement initial eLoran services in other regions around the GLA service area.
The GLA aim to do this in two stages. In the first stage Initial Operational Capability (IOC) service will be installed by mid-2014, with the second stage Full Operational Capability (FOC) service covering all major ports in the UK and Ireland, plus Traffic Separation Schemes, installed by 2019 or so in time for e-Navigation.
Initial Operational Capability
IOC involves upgrading the installation at Harwich and Felixstowe and new installations in the approaches to another six of the busiest ports in the UK: Aberdeen, Grangemouth, Middlesbrough, Immingham, Tilbury, and Dover. For each of these areas an ASF survey and a DLoran reference station will be required.
The corrections for these reference stations will be broadcast using the Anthorn Loran Data Channel. There is also the need for a Monitoring and Control System for the network of DLoran Reference Stations, and it is envisaged that this will be based in Harwich. Figure 5 illustrates the architecture of the Initial Operational Capability system. The diagram shows the major components: eLoran transmitter, DLoran reference station network, monitor, and control system. Also shown are the interfaces between the components, which provide not only operational data but also include the ability to monitor the integrity of the system. Also note that the Loran Data Channel is capable of supporting third-party messaging applications using a client “logon” facility. This is already being done at Anthorn.
Figure 5. The architecture of the UK GLA’s eLoran Initial Operational Capability.
The European tender process for seven operational reference stations and the control system is almost complete.
The aim of IOC is to provide areas for demonstrations and trials, so that the mariner can gain experience of the system and its capabilities and provide feedback to the GLA on its performance.
eLoran at the Port of Dover
In the absence of the final operational reference stations, the GLA decided to perform an early implementation using prototype equipment that was already available at the GLA. The choice for this implementation was obvious: the iconic Port of Dover, a major port on the southeast coast of the UK and the Dover Strait, one of the busiest seaways in the world. Some 500-plus vessels travel through the Strait each day on their way to or from the North Sea region; see Opening Figure.
The GLA have, with the agreement of Port of Dover Operations, installed a prototype DLoran Reference Station within the port’s Terminal Control building. The roof of the building is an ideal location for the reference station receiver antenna as the location demonstrates low noise in the eLoran band and has easy access to mains power, cable runs, antenna mounts, and Internet access.
The ASF survey took place in March 2012, and covers the area outlined by the yellow polygon in Figure 6.
Figure 6. Area of March 2012 ASF survey.
Accuracy Performance Validation
Once the ASFs had been measured and the prototype reference station installed, the performance needed to be tested. This was accomplished through a validation run of the vessel through the area.
Figure 7 shows a screenshot of the GLA ASF measurement software running in validation mode. The colored track shows the path of the vessel, with the color indicating the positioning error compared to differential GPS. The vessel travels through an area of extrapolated and interpolated ASF data, so the positioning error at the northern end of the track is higher than the lower end of the track.
Figure 7. Screenshot of GLA ASF measurement software running in validation mode.
Figure 8 shows a comparison of eLoran positioning against DGPS positioning along the route as a scatter plot. The associated Cumulative Distribution Function (CDF) is shown on the right of the diagram. From this it can be seen that the positioning accuracy obtained along this particular route was 12.5 meters (95 percent).
Figure 8. eLoran positioning accuracy scatter plot and cumulative distribution function of positioning error. Accuracy: 12.5 m (95%)
Dover to Calais Ferry Installation. Further validation and demonstrations will take place aboard a cross-Channel ferry. P&O Ferries in the UK has installed a receiver aboard their vessel, The Spirit of Britain. This relatively new vessel is one of the largest passenger ships to operate along the iconic Dover to Calais route. Data will be collected and feedback obtained on the eLoran service’s performance over the coming months.
Other Areas
The GLA continue their work towards IOC-level eLoran. Dover was the first port of call for the GLA eLoran Initial Operational Capability — the ASFs have been mapped and a prototype DLoran reference station has been installed. The final operational DLoran reference stations should be available this time next year.
The next area the GLA have concentrated upon is the Thames Estuary up to Tilbury. Although the GLA have not yet installed a permanent DLoran reference station, the ASF survey was performed in November 2012 using a temporary reference station installed at Medway. Along the route shown in Figure 9, a validation trial demonstrated 8.3 meters (95 percent) accuracy (Figure 10). The GLA have also recently surveyed the River Humber, including its approaches, up to the port of Hull. The data is currently in the process of being validated.
Figure 9. ASF map validation route from the port of Medway heading out of the River Thames estuary.Figure 10. eLoran positioning accuracy scatter plot and cumulative distribution function of positioning error. Accuracy: 8.3 m (95%).
Status and Next Steps
The next steps are to continue the implementation of IOC eLoran at the remaining port approaches for this phase. It is the aim that all ASF surveys will have been performed by the middle of 2014 in readiness for the installation of the operational DLoran reference stations at each candidate port. Licence agreements are being established with the various port authorities involved in order to allow this.
All ports that have been approached are positive and are keen to assist in the GLA eLoran implementations. eLoran noise surveys have been performed at all ports and locations for all DLoran reference stations have been found.
The Port of Dover has prototype eLoran up and running and has demonstrated 12.5-meter (95 percent) accuracy during the limited validation performed so far; however, further validation continues aboard the Spirit of Britain ferry.
The Thames Estuary ASF Survey has been performed, and 8-meter (95 percent) accuracy has been demonstrated in the area. The River Humber and its approaches have also been surveyed with validation in progress.
IOC-level DLoran reference stations should be available mid-2014, ready for installation.
The methods and processes employed during this work will be proposed for inclusion within the next version of the eLoran receiver Minimum Performance Specification as determined by Radio Technical Commission for Maritime Services (RTCM) Special Committee 27. These include techniques and algorithms used for ASF measurement processing, the preferred ASF file format, guidelines on the usage of ASF data, and integrity computation.
Acknowledgments
The GLA acknowledge the assistance of the crew of THV Alert, the Dover Harbour Board, Peel Ports (Medway), Associated British Ports (Humber), Aberdeen Harbour Authority, Forth Ports, PD Ports (Middlesbrough).
This article is based on a presentation made at the Institute of Navigation International Technical Meeting, January 2013, in San Diego, California.
Paul Williams is a principal development engineer with the Research and Radionavigation Directorate of the GLA, and technical lead of the GLA’s eLoran Work Programme, responsible for the ongoing roll-out of the GLA’s eLoran Initial Operational Capability (IOC). He holds a Ph.D. in electronic engineering from the University of Wales.
Chris Hargreaves is is a research and development engineer with the Research and Radionavigation Directorate Directorate of the GLA. His work focuses on eLoran in measurement trials, software development, and data analysis. He holds a masters’ degrees in mathematics and physics from the University of Durham and in navigation technology from the University of Nottingham.
Aeroflex Incorporated, a wholly owned subsidiary of Aeroflex Holding Corp., has announced its capability to simulate WAAS (Wide Area Augmentation System) LPV (Localizer Performance with Vertical Guidance) approaches by adding this new feature to their GPSG-1000 Portable GPS Simulator.
Aeroflex has developed the capability of simulating WAAS LPV approaches to expedite and validate the installation of WAAS-enabled navigation systems in aircraft. The GPSG-1000 offers the following features to installers of these systems:
Ability to perform structured, repeatable dynamic motion tests (actual flight) of a WAAS/LPV installation,
Ability to check and validate the sensitivity and dynamic range of an airborne GPS receiver, either statically or while in motion,
Reduce aircraft down time and flight demonstration time required by FAA,
Additional support data for documenting proper FAA processes of WAAS/LPV system upgrades or installs without leaving the hangar.
New orders for the GPSG-1000 are ready for immediate delivery. For existing GPSG-1000 customers, a no-charge software upgrade will be available by mid-April 2013.
The FAA created the WAAS program in 1992 to provide the necessary integrity to utilize GPS signals for precision approach. The WAAS consists of a network of precisely surveyed wide area reference stations (WRS). These reference stations monitor GPS satellites to determine errors in the GPS satellite signal. Each reference station relays the information about the GPS satellites to the WAAS wide area master stations (WMS). The master station then develops corrections to the GPS position information and provides timely notification of unreliable GPS data. These corrections are sent to ground uplink stations (GUS) where they are transmitted in the form of a WAAS correction message to a Geostationary Earth Orbit (GEO) satellite. The WAAS signal is then broadcast to users on the same frequency as GPS. This WAAS corrected signal provides three-dimensional guidance to aircraft.
Video VBOX Waterproof by Racelogic combines a powerful GPS data logger with a high-quality multi-camera video recorder and real-time graphics engine, allowing users to carry out detailed driver training and vehicle analysis whatever the weather. Housed in a water-resistant anodized aluminium casing (IP66), Video VBOX Waterproof incorporates a flange and mounting holes to permit users to bolt the system anywhere on their vehicle.
The unit takes video from up to two bullet cameras and combines it with a customizable graphical overlay, recorded on to SD card or USB stick in DVD quality. It is designed for a variety of applications from automotive testing to motorsport, driver training, and industrial applications.
The TraceME micro by KCS BV is a small GPS / GPRS tracker that fits inside a key chain. It is targeted for personal use and any application that need a minimum size while maintaining the exact same options and server connection full-size units have. KCS TraceME GPS / GPRS modules enable remote tracking of objects such as cars, trucks, containers, and motorcycles.
Equipped with a 65-channel Skytraq Venus634LPx GPS receiver, the KCS TraceME Module provides reliable and accurate navigational data. All communication is handled rapidly and effectively by a GPRS/GSM modem (quad-band) through GPRS or SMS. In areas without network coverage, position data and events are stored in memory (up to 55,000 positions). As soon as communication is restored, all information can be transmitted. The user-configuration menu controls actions such as sending position information, depending on all possible events. All of the necessary server-side scripts to process and store data from the TraceME units are available free of charge.
Evaluation Kit NV08C-EVK-CSM by NVS Technologies is a set of instruments for a developer of systems based on NVS Technologies’ NV08C-CSM module. Use of EVK-CSM is a convenient way to learn functionality of NV08C-CSM and begin system design.
The EVK-CSM may be used in navigation systems to obtain the current position (latitude, longitude and elevation), velocity vector, and time GNSS signals including GPS, GLONASS, Galileo, Compass, and SBAS in any location on Earth and at any time. The EVK-CSM is a flexible tool that allows users to evaluate various modes of operation of the NV08C-CSM and to override a default configuration and connection diagram with jumpers.
Connectors and jumpers on EVK-CSM PCB provide simple monitoring of intermediate signals and parameters (digital IOs state, power supply voltages, and currents on individual supply inputs).
OS for Improved Accuracy, EDAS for Further Enhancement, Integrity Data
EGNOS availability over Europe, as a precursor of Galileo globally, provides a guaranteed level of positioning accuracy in real time, for tracking vehicles transporting hazardous material. The EGNOS Open Service enhances position accuracy compared to GPS-only. The EGNOS Data Access Service further enhances accuracy and indicates the quality of the position data received from GPS. As a result of the SCUTUM project, EGNOS is now used in the operational transport of dangerous goods by road in Europe.
By Antonella Di Fazio, Daniele Bettinelli, and Kyle O’Keefe
The road sector is among the largest markets for GNSS applications, not only in automotive mass-market but also in professional applications such as freight transport and logistics. Carrying goods by road naturally involves the risk of traffic accidents. If the goods are dangerous, there is also the risk of incidents, such as hazardous spills, fire, explosion, chemical burn, or environmental damage. The many different kinds of authorities and operators active in the field have safety as a primary concern and make continuous efforts in this regard. To ensure that such transport continues being profitable and logistically effective, emphasis is placed on the quality and condition of infrastructure, on transport safety, and on supervision and control.
Technology’s role, particularly that of GNSS, is to provide the capability of supervision and surveillance, and thus enable better incident management and proactive prevention of accidents, while enhancing work. Use of GNSS combined with sensors and wireless devices has rapidly increased to enable continuous tracking and tracing services. GNSS-tracking devices installed on board vehicles ensure that the position, the date and time, the speed and the course, and any deviation with respect to a predefined path (coordinates and time) are transmitted automatically to a monitoring center. Combined with sensors, such devices send positioning information and the critical status parameters of the material (depending on the nature of the transported material and sensor type: identification of the goods/packaging, temperature, pressure, tampering or valve opening, and so on).
At the monitoring center, positions are displayed on digital maps, and regular data reports are processed for:
continuous tracking and tracing,
control of the shipment in a specified route (according to the plan and authorized path),
early warning/alarm when an anomaly condition is detected,
recording and logging for a regular summary of reported incidents, and
informing emergency-response forces for preparation of management arrangements and supporting emergency response plans.
These operations help reduce the possibility of human error during transport, prevent incidents, enforce regulations, and support law enforcement.
The European Geostationary Navigation Overlay Service (EGNOS), a satellite-based augmentation system (SBAS), augments the GPS signal over Europe and provides more precise positioning services. In addition, it gives users information on the reliability of the GPS signals (integrity data).
EGNOS is designed for safety-critical civil aviation operations. The characteristics of the EGNOS signal are compliant with Radio Technical Commission for Aeronautics Minimum Operational Performance Standards (RTCA MOPS) for airborne navigation equipment using the GPS augmented by SBAS. EGNOS also allows multimodal/land transport applications; however, EGNOS optimal use in these applications requires specific customizations for environments not compliant to MOPS.
The majority of receivers available on the market and integrated in operational devices are EGNOS-enabled. EGNOS provides two services suitable for multimodal/land transport applications:
EGNOS Open Service (OS) is made available to users equipped with GPS/EGNOS receivers, via the satellites’ Signal in Space (SiS).
EGNOS Data Access Service (EDAS) consists of a server that gets the data directly from EGNOS and distributes it in real time to professional users via terrestrial networks, within guaranteed delay, security, and performance.
Software solutions and technologies capable of using EDAS and able to deliver added-value services for road applications have been developed in various European projects in the past several years, have been extensively proven in real life, and are presently ready for operational use. During the last seven years, capitalizing on the efforts of national/European projects and company investments, Telespazio has developed LoCation Server (LCS) navigation software based on a patented algorithm, suitable for combined use of EGNOS OS/EDAS in road applications. LCS makes use of EDAS to augment EGNOS OS performance by:
improving the availability of EGNOS OS, since EGNOS SBAS corrections are made available to users through terrestrial networks and thus also in the cases of poor SiS visibility or complete absence;
enhancing EGNOS OS position accuracy using the patented software navigation solution to implement EGNOS SBAS corrections; and
processing EGNOS integrity information to compute the protection levels that give a qualification and a level of confidence in the position information. LCS is configured to output horizontal protection level (HPL) and vertical protection level (VPL).
Between October 2010 and November 2011, the European project SeCUring the EU GNSS adopTion in the dangeroUs Material transport (SCUTUM) conducted an extensive trial campaign in various road environments (urban and extra-urban) and real operation scenarios, to assess the performances of EGNOS OS and EDAS in comparison with GPS-only. SCUTUM trials were carried out with GPS/EGNOS receivers available on the market for automotive applications.
Analysis of the data collected during the trials shows that EGNOS OS enhances GPS position accuracy by 3 meters in road environments (see Figure 1). EDAS via LCS enables improvements over EGNOS OS by increasing the availability of SBAS corrections, further enhancing GPS position accuracy. Moreover, it affords the possibility of qualifying and guaranteeing GPS position information by exploiting EGNOS integrity and computing the protection levels.
Figure 1A. The green line indicates the reference trajectory; the position obtained by using EDAS with LCS (yellow dot) is more accurate with respect to the position obtained by using EGNOS OS (red dot) and the position obtained by using GPS only (blue dot).Figure 1B. A snapshot displaying the HPL computed by using EDAS with LCS.
SCUTUM Goods Tracking
Funded by the European Commission and managed by the European GNSS Agency (GSA), SCUTUM is the European best practice for the operational adoption of EGNOS in the transport of dangerous goods. An Italian oil company, eni, has had the opportunity to prove EGNOS added value compared to GPS alone, and to validate the relevant operational benefits in terms of higher safety and efficiency. The company adopted EGNOS to track and trace its operational fleet transporting dangerous goods throughout Europe. At the end of SCUTUM’s project timeline in November 2011, more than 300 eni tankers transporting hydrocarbon and chemical products in seven European countries were monitored with EGNOS. Today eni plans to gradually extend the use of EGNOS to the transport of chemicals and aviation products, and to further European countries.
Sensors installed on the trailer to record load status.OBU on the tanker integrating a GPS/EGNOS receiver.
The tankers (see opening photo) are equipped with GPS/EGNOS tracking devices, consisting of a set of sensors installed on the trailer to record the status of the loads. The sensors are connected to an onboard unit (OBU) installed on the truck that integrates a GPS/EGNOS receiver configured to use EGNOS OS. The OBU collects measurements from the sensors, detects information on the vehicle’s parameters, measures the GPS/EGNOS position, and sends this set of data via a GPRS link to a remote monitoring platform (the transport integrated platform, or TIP) enhanced by LCS to use EDAS. The TIP receives the data from LCS, that is, EGNOS positions (corrected by EGNOS OS if available or corrected by EDAS), the relevant HPL and VPL, and visualizes them as shown in Figure 2.
Figure 2. Operational tanker remotely monitored at the TIP by EDAS via LCS.
LCS for EDAS Services
LCS consists of several software modules, among them a module connecting to EDAS to get EGNOS data, and a module implementing the navigation solution by means of the Telespazio algorithm.
LCS makes use of EGNOS SBAS messages plus GPS ephemerides received in real time from EDAS (using Service Level 1), the positions (GPS or EGNOS OS positions when available) and time, and raw GPS measurements (code ranges) from the GPS/EGNOS receiver integrated in the OBU.
LCS calculates and returns EGNOS corrected positions (also in case of lack of SiS visibility) and the relevant protection levels obtained by processing the EGNOS integrity message. The HPL/VPL give a guarantee of the position information from the GPS/EGNOS receiver, as they qualify the reliability of position information and provide a measure of the confidence of the reliability.
If the position data from the OBU is not corrected with EGNOS OS (via the SiS), LCS uses the SBAS messages plus the GPS ephemerides, calculates and applies SBAS corrections, then calculates HPL/VPL. If the position data from the OBU is corrected with EGNOS OS (via the SiS), LCS returns only the HPL/VPL.
For remote monitoring of transported dangerous goods, the features provided by EDAS via LCS (better accuracy, higher confidence on the position, enhanced availability) are considered valuable by eni, as they enable tracking tankers more precisely and reliably along delivery routes, and also from bay to bay (Figure 3).
Figure 3. Accurate remote monitoring of a tanker in a bay area.
At the OBU, the positions are combined with other collected parameters, such as speed, engine parameters, driving parameters, loading/unloading the product on the vehicle, quantity of goods on the vehicle, product temperature and pressure, opening/closing bottom valves and manholes, opening/closing loading station. The information is sent to the TIP and visualized to the local operator, and also forwarded to the eni emergency room (shown in Figure 4) that is connected to the fire brigades and civil-protection emergency centers.
Figure 4. eni emergency room.
In an abnormal situation, such as the vehicle deviating from its planned path or being located in a dangerous/sensitive area, the local operator raises a warning and establishes a contact with the driver. If an accident occurs, an alarm is generated also at the eni emergency room responsible for emergency management and coordinating search-and-rescue operations with the proper public entities. The information is also used to keep the involved transport operator and eni’s customers informed.
Additionally, this information is stored for law enforcement and prevention purposes. Position data and parameters are analyzed to produce statistics and study cases of near-miss accidents.
Benefits generated from EGNOS lie primarily in the capability to implement more accurate risk management and to strengthen safety and prevention. The higher precision with respect to GPS alone and the location achieved by using EDAS via LCS ensure more accurate and reliable monitoring of operations in normal and critical situations, and thus are valuable for commercial purposes and safety reasons. Moreover, eni considers the position guarantee given by the protection levels useful for research on accident prevention.
Multipath-Mitigation Algorithm in LCS
SCUTUM also implemented and tested a multipath-mitigation algorithm used to enhance LCS, to further mitigate the effects of code multipath, typical of land applications. Developed in cooperation with the University of Calgary, the algorithm is based on a fault detection and exclusion (FDE) method and is designed to ensure that biased/multipath-affected observations do not contaminate the navigation solution.
As SCUTUM deals with a road transport application, the assessment targeted the HPL only. The algorithm is based on a statistical-empirical concept combining:
an FDE procedure using a statistical reliability method for the detection and removal of code-range observations corrupted by multipath; and
a field-testing procedure using the receiver under study and a geodetic-quality receiver to produce a reference trajectory.
The FDE procedure consists of sequential steps:
Computation of the navigation solution by means of a least-squares solution to obtain the calculated position, the HPL, and the residuals;
Reliability testing on the residuals, to detect the outliers (observations that contain biases and thus are considered measurements affected by multipath errors);
Exclusion of the detected outliers and re-computation of the navigation solution;
Iteration of the steps. In each iteration, the observation with the largest residual flagged as an outliner is removed.
The procedure ends once no further outliers are isolated, or the number of remaining observations is less or equal to five, or several special-case conditions occur. Outlier detection is done on the basis of a rejection threshold on the standardized residual. This rejection threshold is a parameter of the multipath-mitigation algorithm and is tuned by means of the field-test results. Additionally the multipath-mitigation algorithm behavior is a function of other parameters that depend on various factors, including satellite elevation, signal strength, and overall satellite geometry.
Field Trials
SCUTUM field trials covered several environmental conditions and LCS configurations. Tests were performed in a wide range of Italian urban and extra-urban road environments. They considered five different typical driving environments (Table 1), corresponding to different levels of GPS and EGNOS signal availability and multipath, and various vehicle speeds and dynamic characteristics, with the objective of testing the robustness of LCS’s navigation solution.
TABLE 1. SCUTUM field trials driving environments.
From a physical point of view, the presence of natural and/or artificial obstacles could lead to lack of GPS and SBAS signals, worse satellite geometry, and introduction of additional errors in the measurements due to multipath propagation effects. Urban canyons are particularly prone to such effects, although they occur also in other cases depending on the topographic characteristics of the environment. For these reasons, the trials covered all possible environments traveled by LCS users, to provide a complete technical and business analysis for each operational condition.
To accurately indentify the appropriate driving environment, trial paths were matched on clutter maps categorizing the different driving environments (as shown in Figure 5 in the example of a trial path in Rome).
Figure 5. Method for driving environment identification by means of a clutter map.
A reference trajectory, hereafter called the true path, was calculated in post-processing, through a kinematic differential GPS method, by using GPS L1 and L2 carrier-phase measurements, combined with inertial navigation system (INS) measurements.
The differential GPS L1 and L2 carrier measurements were collected with a reference receiver installed near each test location, at an inter-receiver distance not exceeding 20 kilometers. The reference receiver was geo-referenced via a dedicated GPS network solution (based on a continuous collection campaign of at least two days’ data). The combination with INS targets smooth trajectories free from jumps, even in difficult GPS environments.
The tests ran on two identical OBUs, one GPS-only and one using GPS+EGNOS. The two OBUs and the GPS/INS system were installed in a test vehicle (Figure 6) and connected to a standard GPS patch antenna for automotive applications. Two pairs of OBUs were used (Figure 7).
Figure 6. GPS/INS system installed in the vehicle.Figure 7. OBUs in test vehicle.
Test Results
The trials collected these data sets:
Raw measurements from the GPS/INS system;
Positions and raw measurements from the two OBUs, GPS and GPS+EGNOS respectively.
As mentioned, positions and raw measurements from the GPS OBU were processed by LCS’s navigation solution in three configurations:
LCS baseline, running the baseline multipath mitigation method (based on the proprietary patented algorithm);
LCS enhanced, applying the multipath-mitigation algorithm with default settings of several parameters;
LCS enhanced and tuned, applying the multipath-mitigation algorithm with tuned parameters. The tuning was obtained by applying the combined statistical-empirical concept described earlier.
Data collected during the field trials was analyzed in terms of:
average values for the horizontal navigation system error (HNSE) that is the horizontal difference of the OBU position with respect to the reference trajectory;
average values for the HPL that gives an indication of the confidence/guarantee of the position above mentioned; and
the availability of the processing of LCS’s navigation solution.
Test data was analyzed with both commercial and freely available software packages. Table 2 reports the performances of LCS in its baseline configuration for each driving environment. Table 3 reports the performances of LCS by means of the multipath-mitigation algorithm with different tunings for extra-urban and urban environments.
TABLE 2. Performances of LCS baseline for driving environments.TABLE 3. Performances of LCS enhanced by multipath mitigation algorithm with different tunings.
The results show that for the road environments tested, LCS baseline performs better than statistical FDE.
From these results, an interesting conclusion can be drawn: in the road environments tested, a traditional FDE approach is not as effective as would be expected. Specifically, the removal of observations with large residuals resulted in larger overall position errors, both before and after attempting to estimate a larger observation variance than normally used for GPS. The reason for this is that in urban environments and extra-urban road environments there is significant multipath, corrupting many observations at the same time that the number of available observations is low. The conclusion is that on average, in the environments tests, it is better to leave small, but still statistically detectable errors in the solution than to remove them and degrade the solution geometry.
The fault-detection approach will be more appropriate in a multi-constellation GNSS, and in particular in the future when Galileo satellites can be used in conjunction with GPS, resulting approximately double the satellite availability in all environments.
Table 4 summarizes average performances for GPS+EDAS using LCS baseline compared with those of the GPS-only and GPS+EGNOS.
TABLE 4. Average performances of GPS+EDAS by means of “LCS baseline” in comparison with GPS-only and GPS+EGNOS OS.
Workshop Agreement
SCUTUM also carried out a European Committee for Standardization (CEN) workshop that elaborated the CEN Workshop Agreement (CWA) 16390:2012, Interface control document for provision of EDAS-based services for tracking and tracing of the transport of goods, that is, the technical specification for development of EDAS-based products and applications.
CWA 16390 specifies:
the data (and relevant format) needed from the GPS/EGNOS receivers by the software solutions connected to EDAS, to enable the implementation of products and added value services; and
the type/format of the added value services produced by the software solutions (EDAS-based services).
The technical specification defined in CWA 16390 is architecture/technology-independent and flexible, so as to:
cope with different architectures (for example, those envisaging software solutions running in the monitoring platforms or in the OBUs); and
ensure its applicability in ITS systems and various mobility applications.
CWA 16390 was endorsed by several European stakeholders from industry, institutions, and the research sector. The Ministries of Transport in Italy and France, partners in the SCUTUM project, validated it as part of a shared vision for EGNOS adoption and exploitation. Italy’s Ministry of Transport is presently carrying out the possible evolution of CWA 16390 into an Italian standard.
Conclusions
SCUTUM represents the first step towards a larger use of EGNOS in Europe for the provision of services for road applications, and opens the market for Galileo. Its key findings are that EGNOS OS generally enhances the position measured using GPS-only in all extra-urban and urban environments. EDAS generally provides further enhancements, and also gives an indication of the quality of the position data received from the GPS.
LCS is a plug-in solution that enables easy retrofitting of existing GPS systems to use EGNOS, but optimized for road applications. By integrating it in tracking and tracing monitoring platforms and configuring the vehicle-installed OBUs, LCS enhances GPS position accuracy by approximately 4 meters and provides a level of confidence in the position information in the form of an HPL and a VPL. LCS will also improve GPS/Galileo integrated solutions when Galileo is operational. Its navigation solution will be more robust with Galileo and in general with multiple constellations, thanks to the availability of more satellites in view.
Manufacturers
A NovAtel FLEXG2-V2-L1L2 served as GPS reference with a NovAtel dual-frequency GPS-702GG antenna. An Oxford Technical Solutions RT2002 dual-frequency GPS/INS system served as rover. The two OBUs integrated a u-blox 5 GPS/EGNOS receiver. In its present configuration, LCS is connected to a dedicated GPS/EGNOS receiver, NovAtel ProPak-V3-L1 acting as EDAS back-up for robustness reasons.
Antonella Di Fazio works in the GNSS Infomobility Business Unit of Telespazio, in charge of innovative applications and services and program and technical coordinator of European R&D projects, devoted to the use of EGNOS/Galileo.
Daniele Bettinelli works in the GNSS Infomobility Business Unit of Telespazio, in charge of the specification, design and development of services based on EGNOS and EDAS, in particular for land applications.
Kyle O’Keefe is an associate professor in the Position, Location And Navigation (PLAN) group of the Department of Geomatics Engineering at the University of Calgary.
Communications Security, Reliability, and Interoperability Council (CSRIC) Update
By Greg Turetsky
Many of us remember way back in 2001 when the FCC first announced E911 position reporting requirements for cell phones. That was a long time ago in many significant ways. Everyone had 2G phones and anxiously anticipated the arrival of 3G, and with it, data. Most people still had a landline at home, and used their mobile sparingly lest they overrun their monthly minutes. Roaming was very expensive and nearly impossible overseas. Very few phones had GPS, and people only turned it on when needed, as it significantly reduced battery life.
Now, in 2013, all of the technology has changed, but — not unexpectedly — the regulations have not. This is one of the reasons the U.S. Federal Communications Commission (FCC) created CSRIC.
The Communications Security, Reliability, and Interoperability Council’s mission is to provide recommendations to the FCC to ensure, among other things, optimal security and reliability of communications systems, including telecommunications, media, and public safety. The current council, CSRIC III, was born on March 19, 2011, and ended on March 18, 2013. Working Group 3 (WG-3), the E911 Location Accuracy group, has looked into both outdoor and indoor location accuracy issues to help the FCC shape new guidelines. I don’t think any of us would argue that given the current patterns of cell phone usage, the ability to provide a location indoors to a public safety answering point (PSAP) is something that is now needed, has significant value to the public, and would seem to lie within our grasp technically.
Working Group 3 is a fairly large group of experts from a wide variety of backgrounds. The actual list of participants is publicly available; what’s more interesting is the groups that they represent. Three main constituencies constitute the Working Group: the public safety community, the wireless operators, and the technology vendors. Each group has a slightly different goal, but they all worked well together to produce clear, unbiased reports that represent all the different members’ views in a way that lends more credibility to the overall report.
On March 14, the FCC released two reports created by WG-3: the “Indoor Location Test Bed Report,” and “Leveraging LBS and Emerging Location Technologies for Indoor Wireless E911 Report.” I will not review either document here as they are available publicly, but I will summarize the highlights of the reports from my perspective as a member of the location community and a concerned citizen, and attempt to predict where the process might lead next.
Figure 1. Indoor accuracy in the dense urban environment.
Test Bed Report. In my mind, two key results emerged from the Test Bed Report. The first was very positive: the test bed showed that there are technologies capable of yielding positions indoors, and their performance can be compared analytically. This may seem like a bland statement, but it carries a significant amount of weight with both the public safety community and the FCC. It acknowledges that the technology has evolved sufficiently such that in a test bed setting, we can gather and compare, in an apples-to-apples way, the performance of diverse technologies in terms of yield and accuracy. Similar to the LightSquared reports, this report focuses on ensuring that the data itself is valid. The interpretation of the data is far too politically and economically charged to be agreed on by all parties involved. It is a great accomplishment to concur on a methodology by which testing should be done, and to produce a set of results that can be given to the FCC with the entire council’s approval.
The second highlight from my perspective was less positive. The test bed originally had seven participants, but in the end only three completed the process. This indicates that there are even more candidate technologies for solving the indoor E911 problem — but for a variety of reasons, they were not ready for CSRIC testing at this juncture. Although having three choices is good, seven (or even more) would be better for the FCC to feel confident in its ability to create a new mandate with sufficient flexibility on implementation. There are clearly many ways to skin this cat technically, but we have to ensure that the test bed methodology allows as many as possible viable alternatives to be compared. There is clearly a gap between those technologies that are commercially available and those that can be used for E911.
Leveraging LBS. The Leveraging LBS Technology report also reached some interesting conclusions. The concept of leveraging LBS was actually how I became involved in the CSRIC. The underlying question that the FCC asked me to explore was “Why can a smartphone user can get a dot on a map indoors (usually with an uncertainty circle, no less), but no location information shows up on the PSAP screen if he makes an E911 call?”
As we dug into this problem, it became clear that this was less of a technology problem and more of a business/policy one. Quite a few large companies make money by providing that indoor location for various applications, but there isn’t any real money in E911 — although there are lots of liabilities. Also, many of these solutions are proprietary either to the phone, the operating system, or the application, while an E911 solution would need to be standardized across all of those as well as different carriers.
Figure 2. Indoor accuracy in the urban environment.
Conclusion. The FCC has received two reports with similar conclusions: We have come a long way since 2001, but we might not be there — the indoor E911 promised land —just yet.
There is still more to come, however. Therefore, many participants and observers hope the work of the current CSRIC will lay the foundation for a rational conversation about indoor E911 right now, and still be around to allow for future improvements. We have recommended that the test bed be maintained so future results can be compared with current ones. At issue is the funding source for the test bed. The FCC has announced the coming of a CSRIC IV, but has not released any further details. It is certainly the hope of WG-3 that the work performed to date to establish and validate the test bed will be available for use by future technologies as they mature.
Locating emergency callers indoors is a critical capability that we as society must address — not for the callers’ convenience, but for their safety and or public safety generally. The problem has technical, commercial, regulatory, financial, legal, and public safety facets to it, making it a very complex issue.
I should also note, that although E911 is a U.S. regulation, the problem of indoor location is under scrutiny in nations all over the world. I earnestly hope that all sides can continue working together to find a solution that can be implemented for the benefit of everyone.
Greg Turetzky is senior director, CTO Office, for CSR. He served on the CSRIC Working Group 3 LBS Subgroup. He will participate in a April 16 GPS World Webinar on this topic. Registration is free.
Furuno Electric Co., Ltd., has announced that new multi-GNSS receiver chips eRideOPUS 6 and eRideOPUS 7 will be available in August. The new receiver chips are multi-GNSS compliant single-chip LSIs, capable of concurrently receiving signals from multiple satellites in GNSS systems and satellite-based augmentation systems, as well as Japan’s Quasi-Zenith Satellite System. Both chips receive signals from GPS and Galileo; the eRideOPUS 7 also receives GLONASS signals.
The ability of concurrently receiving GNSS/GNSS augmentation signals from multiple satellites from different satellite services means that the receivers have more probability of acquiring a greater number of satellites at any single time. Subsequently, position stability as well as accuracy will be greatly improved, minimizing the chance of a position lost. Also, the receiver chips incorporate an enhanced level of noise rejection capability, implementing the anti-jamming function as well as the improvement of multipath mitigation.
Time-to-first-fix capability of the existing eRideOPUS 5 (no more than 1 second when hot started) is retained in these new receiver chips with a combination of A-GPS compatibility and self-ephemeris extraction. Moreover, the position update rate of the new receiver chips is greatly improved, achieving a 10-Hz update (every 0.1 second), which is twice as fast as the capability achieved by eRideOPUS 5.
The new receiver chips are capable of dead-reckoning navigation, using a gyro sensor and vehicle speed pulse signals, a gyro sensor and an acceleration sensor, and wheel tick data taken from a CAN-Bus network, achieving high positioning accuracy even in locations where satellite signal reception is not available, such as inside tunnels.
In May 2013, Furuno is planning to start the delivery of evaluation kits for the receiver chips so that third-party manufacturers can evaluate the feasibility of incorporating the receiver chips into their products, and in August 2013, the new compact GNSS receiver module GN-86/GN-87 as well as
dead-reckoning-capable GV-86/GV-87, using these new receiver chips, will be made available for automotive navigation systems as well as eCall systems.
