Navigation – Current Challenges
Experts across the globe discussed current challenges before navigation at International Navigation Conference held at Manchester, UK during February 24 – 26, 2015. We present here some of the views
Divide between Vulnerability and Autonomy
The International Navigation Conference 2015 marked the return of the Royal Institute of Navigation to the business of organising major navigation meetings. For some years they have waited on the sidelines as too many conferences competed for a declining number of delegates. This gathering, despite its being scheduled for Manchester in February, attracted 200 attendees. It was small enough to be collegiate and informal while large enough to pull in the great speakers: just imagine, Dana Goward and Todd Humphreys on one bill! RIN conferences have always been informal, welcoming of debate, very open to differences of opinion. And in Manchester those differences were so great, and the shifts of attitude so substantial, that I suspect we will look back on INC2015 as a moment of change.
RIN conferences are different, too, in being about navigation, not just satellite technology. Here we had papers on marine developments including the ACCSEAS studies of eNavigation (Alwyn Williams), decision support systems (Zbigniew Pietrzykowsk) and even flashing lights (Malcolm Nicholson). There was Quantum Technology (Leon Lobo) and a raft of indoor systems. The breadth was outstanding.
The conference opened in the traditional manner of navigation conferences in Europe. A US speaker (Ray Clore) gave an update on the status of GPS and a Brussels chap (Gian Gherado Calini) countered with Galileo. They spoke of separate competing systems, each vertically-integrated – with satellites, receivers, applications and users – overseen by an administration. GPS markets and Galileo markets were assessed. Underlying the subsequent discussions were concerns about the threat of Galileo’s being mandated in Europe and the recent “bombshell”: that the reception of “foreign” GNSS in the US might be illegal, inappropriate for public services, and even un-American!
RIN Past-President Colin Beatty then gave a contrary world-view. Galileo will soon be merely 30 satellites among maybe 150. Receiver chips already accommodate all these systems plus multiple augmentations; the receiver designers are well ahead of the satellite launchers. Receivers now use these many signals to deliver the best possible PNT. And their users neither know nor care about GPS or Galileo any more; they don’t even realise their iPhones are using GLONASS. Mandating systems will mean denying users the benefits of multiple GNSS! Which world-view will prevail?
Then another division opened up: between Vulnerability and Autonomy. The “Vulnerablists” declared that GNSS is fallible and dependent on weak signals, easily disrupted by noise and interference, some natural, some accidental and some – jamming and spoofing – malicious. You should not rely on GNSS but back it up with a different but complementary system. The clear leader here was eLoran which the UK General Lighthouse Authorities now had up and running, serving mariners (Gerard Offermans) and precise timing users (Charles Curry).
The “Autonomists” explored the contrary view. All is well. The combination of GNSS with mode-specific sensors and advanced computer systems is now sufficient to support autonomous cars (Neda Navidi), autonomous ships (Andy Higgins) and even pilotless passenger aircraft (Lambert Dopping-Hepenstal). Given the conflict between these two world-views, it was probably wise of the RIN to schedule them into parallel sessions, so physically separating the protagonists!
Two yawning divides: the first between those who believe in rival satellite systems, centrally organised, and those for whom systems are now just components of GNSS with the receiver makers determining the mix. The second divide, between the Vulnerablists and the Autonomists, is turning into a sort of Global Warming of the navigation world, with proponents and deniers locking horns! I predict that after Manchester these two conflicts will dominate navigation conferences for quite some time.
Today’s challenge is to develop a Robust PNT package
For has long as mankind has roamed the earth there have been those among them who became specialists in the art of knowing where they were and how they were going to get to their destination. Various devices were developed to help them in their journeys including the magnetic compass and methods of measuring the angles of heavenly bodies above the horizon. The greatest challenge was the determination of accurate time to allow Longitude to be deduced. It was Harrison who solved the problem of building a clock that could withstand the rigors of ships’ motion. Navigation on long ocean voyages out of sight of land, became much more reliable.
In the early 20th Century, Elmer Sperry and Sydney Brown each developed gyroscopic compasses that provided much more reliable and accurate determination of North direction. Radio Direction finders were used at sea and in the air to provide bearings to radio transmitters whose positions were known. During World War II radio hyperbolic and ranging systems were developed for ships and aircraft. It was really after WWII that electronic radio navigation became available to the civilian navigator. Loran , Decca Navigator and Omega were the navigation systems of the 50’s, 60’s and early 1970’s.
As demands for accuracy increased various local area navigation systems were developed.
A key breakthrough came with the introduction of the US Navy Navigation Satellite System, TRANSIT. This provided between 35 and 150metres accuracy with fixes occurring every 1-4 hours depending on the user’s latitude. Development of yet another satellitebased system, the Global Positioning Sytem (GPS), started in the 1960’s with the first satellites being launched towards the end of the 1970’s.
Even before GPS became fully operational, there was an unseemly rush to shut down the old radio navigation systems. We were told that GPS would solve all of our positioning and navigational problems. The accuracy obtainable with GPS was amazing to the point where the US Military applied a Denial of Accuracy (Selective Availability – SA) to the civilian code. It took but a couple of weeks before the effects of SA were largely circumvented by the development of Differential GPS. Thus, the civil community could now navigate at the 5-10 metre level of accuracy.
Up until the arrival of the in-car satellite navigation systems (satnav) and Smart phones, navigation had, very largely, been the preserve of specialist navigators. These were the people able to use sextants and radio-navigation systems to determine their location. It was necessary to study and to take examinations for to get your navigators “ticket”.
For a number of years it really looked as if GPS and similar systems, the Russian GLONASS, the European Galileo and the Chinese Bidou would be all that was needed for reliable navigation. Unfortunately, due to the nature of these satellite-based systems, their signals, as received on Earth, are very weak. This makes all of the satellitebased navigation systems vulnerable to both accidental and purposeful jamming. It is possible to purchase, off the Internet, low cost jamming devices that effectively swamp the radio signal coming from the satellites. Just a few Dollars is all that it takes. In the past couple of years, the vulnerability of Global Navigation Satellite Systems (GNSS) has come to the forefront.
At the recent Royal Institute of Navigation’s International Navigation Conference, held in Manchester, UK, a number of the presentations addressed the issues of the vulnerability of GNSS. Papers were presented that highlighted the need for much more robust GNSS to cover the three areas for which GNSS is now used, Position – Navigation and Time PNT. Several eminent specialists, among whom is Professor Brad Parkinson, have called for the adoption of RPNT – Robust Position, Navigation and Timing.
RPNT requires a number of areas of research and development to refine the design of GNSS receivers. Certain of these solutions integrate other navigation sensors to aid the GNSS and thus help tackle the effects of jamming. Devices such as Inertial Measurement Units (IMU) and other radio-navigation systems, such as eLORAN, have been suggested. eLORAN is an enhanced version of the old LORAN system that served a number of local areas, around the world, for many years. Only within the last year has the USA been decommissioning their old LORAN stations, a move that has recently been halted. eLORAN, being a terrestrially based system has a much higher power level making jamming somewhat more difficult. Whereas the GNSS signals have frequencies in the 1.5 – 1.6 GHz bands, eLORAN is down at 100KHz, a totally different area of the radio-frequency spectrum.
Today’s challenge is to develop an RPNT package that will be resilient under the threat of jamming. Also to be considered is the requirement to make these new navigation systems able to resist spoofing. With fairly sophisticated equipment, it is possible to spoof a GNSS receiver to put it into an erroneous position, in error by many miles. This is particularly serious when GNSS is used to determine the altitude of aircraft in its final approach to an airfield. Multi constellation receivers make such spoofing more difficult – but not impossible. There is much work to be done.
The multisensory approach is likely to be the future of the navigation systems
The demand for accurate, reliable and resilient navigation and positioning information, not only in the traditional open-sky environments, but predominantly in confined and transition environments, where the availability of GNSS signals is compromised, has been the primary innovation driver in the positioning, navigation and timing (PNT) industry in recent years. The designers and manufacturers of the navigation equipment as well as the policy makers face formidable challenges, as they must accommodate many, at times seemingly contradicting objectives. A fundamental challenge that GNSS, a backbone of the majority of the contemporary navigation systems, is facing, is the fiscal challenge: how much governments are willing to spend on GNSS, and will the budgetary support be assured, continuous and sufficient? Directly connected is the challenge to internationally manage GNSS in a transparent, coordinated, comprehensive and equitable way. While the cooperation established via the International Committee on GNSS is an excellent start towards addressing this challenge, more needs to be done by the governments and professional organizations to assure sustainability of the constellation and protection of the GNSS spectrum against interference, jamming and cyber attacks. To assure that GNSS and related industries continue investing in the location and navigation markets, GNSS legislators, regulatory agencies and professional communities, as well as the industry must work together to address these challenges. A closely connected challenge is the lack of a GNSS back-up system, a topic of an ongoing debate among professional organizations, the governments and the users. Consumer demand is driving a surge of innovation, and since GNSS cannot fully cover all of the users’ demands, the last decade or so has witnessed substantial intellectual and monetary investments in multisensor integrated navigation systems. As obvious as the mutisensor approach might appear, it introduces a number of new challenges, focused primarily on how to integrate different technologies in the cost effective manner, without compromising the integrity and design principles of the contributing technologies, and avoiding high complexity of the resulting system. A substantial body of research has been generated in recent years, towards the design and implementation of multisensor navigation systems, where initially the sensors were loosely integrated, and recently, with a more coordinated effort of the contributing manufacturers, the systems are becoming more tightly integrated, offering a clear benefit of better information sharing and improved exploitation of complementarity and redundancy features. The prime example is the evolution of the GNSS/inertial integration from a loosely coupled system, to the ultra-tightly coupled approach, where GNSS receiver is implemented as a software-defined radio, whose tracking loops are aided by the inertial system.
The multisensory approach is likely to be the future of the navigation systems, with more sensors, increasingly unconventional (i.e., not designed for navigation, such as imaging systems), coalescing into a multifaceted system. Different types and varying numbers of sensors integrated together contribute to the complexity of the system, and, consequently, the current challenge becomes the effective system design. The target of this challenge is modularity. In modular designs sub-system functionalities are separated into discrete, scalable and reusable components. The concept of plug-and-play is a perfect example of a high-level, flexible modular design, where an obvious benefit is the augmentation achieved by adding a new solution by plugging in a new or updated module. This approach, however, requires the use of not only advanced integration algorithms and well-defined modular interfaces, but also a rigorous use of industry standards for interfaces. In addition to the need to address the modularity, miniaturization and portability, combined with the requirement for high accuracy and low cost, and the adaptability to different requirements of various user communities is yet another challenge that the navigation and location industries are presently facing.
New technologies drive new applications and new applications create new challenges. With challenges come opportunities. One example – the Location Based Services (LBS) – the fastest growing sector of PNT applications. Aside from the location privacy challenge that comes with LBS, tremendous opportunities are being generated for many markets, with Asia leading the pack. According to the 2013 GNSS Market Report, the global GNSS market growth in terms of CAGR is expected to reach ~21% over the period 2012-2016, with the LBS only revenues expected to reach over 80 billion Euro by 2020. Autonomous vehicles application that requires not only reliable and high accuracy navigation information, but must also assure that the vehicles will sense their environment using a suite of active and passive imaging sensors. Once the regulatory policies are in place for safe introduction of these vehicles to our roads and airspace, navigation industry must be ready to deliver suitable multisensory navigation and imaging systems that are not only lightweight but also lowcost and more accurate than most of the currently available portable devices.
The navigation industry has been a game-changer by driving the innovation and working towards affordable, accurate, resilient and ubiquitous navigation information, and enabling new and emerging applications, such as autonomous vehicles, pedestrian and asset tracking, emergency response and rescue operations, fast detection of catastrophic events, LBS, precision farming, just to name a few. PNT is delivered via dedicated and ad hoc infrastructure, such as the GNSS constellation, ground and space augmentation, other RFbased systems, signals of opportunity, imagery, digital elevation models, etc. The primary challenge to delivering ubiquitous PNT is in the areas with no infrastructure, where only the sensors carried by the user or a group of users (collaborative navigation) can be used.
In summary, no single sensor currently available is able to provide the required level of accuracy, continuity, portability and security of PNT in all environments. Thus, integrated systems are the likely future of navigation, with multi-system and multisensor generalizations decreasing vulnerability against system failure and attack.
As requirements and performance standards are constantly on the rise, navigation faces new challenges
The perception of navigation has changed over the last decade. The factors responsible for this change are modern technologies, including information and communication technologies (IT, ICT), and new areas of application. Navigational systems and equipment have become easily available, and are used by small groups of specialists and innumerable individual users. As requirements and performance standards are constantly on the rise, navigation faces new challenges.
The primary function of navigation is positioning and indicating the direction from one specific point to another. Although from the viewpoint of services offered, navigation performs mainly information functions, decision support is another function of gradually extended scope. Both functions are also applicable to autonomous, unmanned vehicles.
The starting point for defining challenges for navigation are basic tasks concerning resilient PNT – Positioning, Navigation and Timing. These tasks are determined by technological capabilities as well as needs resulting from human activities. In reality we seek new applications for stateof the-art technologies on the one hand, and attempt to develop new technologies to satisfy users’ demands on the other.
It seems that at present IT, ICT and nanotechnologies are of key importance. IT and ICT spur the development of GNSS and other alternative positioning systems, and contribute to the enhancement of information systems (gathering, processing, retrieval and presentation of navigational information) as well as decision support systems. Micro- and nanotechnologies increasingly miniaturize sensors, navigational equipment and entire systems.
Areas of use
Navigational systems are used in various sectors of economy, including transport (marine, air, car, pedestrian), industry, commerce. More and more attention is paid to pedestrian navigation (sport and tourism), indoor, offshore and underwater (exploitation of the sea and ocean resources) as well as space navigation (space transport, space tourism). Most of the above cases involve access to information and decision support, including autonomous systems for unmanned vehicles, some of which have important military applications.
Regarding information, requirements mainly comprise accuracy, validity and credibility. Requirements for real time systems and devices include safety, availability, reliability and security. On this basis, we can attempt to define current challenges for navigation in terms of Positioning, Navigation and Timing.
The relevant challenges are aimed to assure high accuracy, validity and credibility of information to raise system availability, reliability and security. These goals entail the use of various navigational systems and devices to provide for system diversity and redundancy. For the former, we have to provide the same functionality in different ways, e.g. apart from the primary positioning system, alternatives should be used. The latter, i.e. system redundancy, requires a critical component to be doubled so that if one component fails, a backup is available.
In both cases the amount of information increases and necessitates data integration and fusion. As the number of sensors is growing, so is the need for data fusion solutions, which allow the system to present more accurate and reliable data on vehicle position and movement parameters. Improvement of the existing and seeking new positioning methods are essential in areas where the known systems prove to perform poorly, e.g. indoor or underwater navigation. One interesting research direction is the study of human and animal abilities to navigate as well as research on cognitive skills (cognitive science).
Threats of external attacks (jamming, spoofing) call for developing methods and tools assuring the availability and/ or accuracy of positioning data.
Growing amount of information available in navigational systems on the one hand permit the operator to fully assess the situation, on the other hand information excess may cause human errors in situation analysis and assessment. That is why information systems evolve towards decision support systems. These, in addition to information functions, are capable of analyzing and assessing a current situation and working out a recommended solution. Knowledge engineering, including artificial intelligence methods and tools are used to equip the system with characteristics normally attributed to humans, such as adaptation, learning, autonomy and complexity. The implementation of decision support systems can significantly reduce the number of human errors, which translates into the reduction of accidents at sea and their adverse consequences. Due to their functions, decision support systems are an essential, often necessary component of autonomous systems for unmanned vehicles: aircraft, sea-going vessels or cars.
Challenges concerning timing are aimed to improve the precision of atomic clocks, enabling more accurate time and frequency synchronization over large distances.
This review of challenges is not complete. It will vary in types and scope depending on further technological advancements, widening range of applications and evolution of user needs.
Current challenges in navigation are increasingly driven by applications and
are less technologically determined
With respect to the navigation market, today we are living in exciting and challenging times. The key drivers for the current navigation market and in future, in our opinion, are still twofold. They are application based on one hand and technology driven on the other. It appears, however, that the current challenges in navigation are increasingly driven by applications and are less technologically determined.
From a technology point of view, the navigation market has already changed from the usage of a single satellite navigation system, primarily GPS, towards the usage of multiple satellite navigation systems, called multi- GNSSs (Global Navigation Satellite Systems). Examples are the combined use of GPS and GLONASS that are present in the consumer market (e.g. in smartphones and for car navigation) and the usage of multi-GNSS (e.g. GPS + GLONASS + Galileo + BeiDou + SBAS + QZSS + IRNSS), combined with multi-frequency in the professional and safety-of-live market.
Current challenges in navigation, from a technology point of view, are more driven by the demand of high-sensitivity capability in combination with external sensors on one hand; and high position accuracy in combination with high reliability and integrity on the other. In this context, in future, it is foreseeable that the use of dual-frequency equipment in the consumer market will also be in demand.
Application based means that the number of applications relying on position, velocity and timing (PVT) information will grow permanently in future, as it has already in the past. Many applications are already using this information today, predominantly derived from worldwide available satellite navigation systems. The growing number of applications demanding such PVT information even under challenging environmental conditions, such as in inner cities, in urban canyons or indoors, will in future also affect and most likely change the technical requirements of the user equipment (GNSS receivers or more generally GNSS positioning sensors). Furthermore, this will influence the usage requirements of the global satellite navigation systems.
From our point of view, current challenges in navigation regarding applications are most likely coming from the foreseeable trend, that safety in combination with security will play a greater role in upcoming applications. Examples of such applications are Autonomous Driver Assistance Systems (ADAS) and Unmanned Autonomous Systems (UAS), such as robots or UAVs (Unmanned Autonomous Vehicles). Besides high position accuracy, these applications require reliable and secure operations of the system. Thus, safety and security aspects will be one of the key requirements for such applications. In addition, the wish of seamless indooroutdoor navigation is still another driver of current challenges in navigation demanded by several applications.
Last but not the least, all these current and future challenges in navigation will also affect the testing requirements for GNSS receivers and positioning sensors, and finally the testing needs for GNSS-based applications. IFEN will be prepared for this current and future challenge in navigation by providing a complete portfolio of leading-edge GNSS test solutions.
“GPS is Too Good”
“The U.S. military has become increasingly dependent upon the Global Positioning System (GPS) for accurate and precise positioning, navigation, and timing in a wide variety of operational environments. However, as U.S. military operations are increasingly carried out in areas where GPS is denied, unreliable, or not accessible, military use of GPS has evolved from strategic advantage to vulnerability. GPS access can now be readily blocked by jamming or environmental conditions … Current system solutions for providing accurate and precise positioning, navigation and timing in GPS-denied environments are costly, inflexible and often need an external fix that requires intermittent access to GPS…”
– United States Defense Advanced
Research Project Agency (DARPA)(http://www.darpa.mil/Our_Work/ STO/Focus_Areas /Positioning_Navigation_and_Timing_%28PNT%29.aspx)
While the DARPA website quoted above was, of course, concerned with military operations, much the same could be said of the civil community as well.
Highly precise and free for use anywhere with a view of the sky, the Global Positioning System (GPS) has been superbly maintained and operated. It has been so reliable and useful that it has made us complacent to the point where navigation-as-we-know-it is no longer possible without GPS. If GPS service were to be disrupted, our current air, maritime, and land transportation systems would be unsustainable. All modes of transportation would slow down and be able to carry less traffic. GPS has become a single point of failure for transportation around the globe.
This isn’t because the superb reliability and accuracy of GPS-based electronic navigation systems has resulted in the loss of other navigational skills, although that is indeed true. But even if mariners were to relearn how to use a sextant and drivers were to buy and figure out how to use road maps (both of which are good ideas), these methods of navigation could not sustain the our current system speeds and efficiencies.
Our real complacency isn’t shown when someone mindlessly goes off the road because their car’s “GPS” tells them “turn right.” Rather it is the fact that there are no non-space electronic navigation sources to fall back that are able to sustain current transportation service levels during a GPS disruption. (Many may argue that this is not true in aviation, and the author agrees that aviation would be less impacted because of legacy navigation aids such as VOR, DME and ILS. However, integration of GPS into on-board and ground systems for both navigation and support services means that a GPS service disruption would degrade the aviation system as well.)
The solution to this complacency, to the problem that “GPS is too good,” is a sensible agenda to protect, toughen and augment our Global Navigation Satellite Systems (GNSS).
Originally proposed by Dr. Brad Parkinson, the man most responsible for development and deployment of GPS, the “Protect, Toughen and Augment” scheme has been adopted by our non-profit. It incorporates recommendations from Dr. Parkinson, the US Positioning, Navigation and Timing Advisory Board, and best practices from around the navigation community.
These recommendations are given in the box on this page, and are also available at the foundation’s website: www.RNTFnd.org.
Protect, Toughen, Augment
Policy Recommendations for Global Navigation Satellite Systems
• Recognize PNT as critical infrastructure
• Designate and empower a lead federal official
• Protect the adjacent bands to GNSS as “quiet” neighborhoods
• Make ownership of jammers a misdemeanor
• Make use of jammers a felony
• Make anti-jamming and anti-spoofing laws enforceable at all levels of government
• Establish a national system to detect & rapidly locate jamming
• Ensure sufficient enforcement personnel to detect,
prevent, respond to and prosecute jamming
Toughen Receivers & Users
• Develop standards for jam-resistant receivers to include ARAIM and RAIM
• Establish as an industry best practice having more than one source of
precise Position, Navigation and Timing (PNT) for critical infrastructure
• For critical infrastructure that uses space-based PNT, establish as
an industry best practice being able to continue normal operations
in the event of an extended GNSS service disruption.
Augment GPS/GNSS Services
• Provide a wide-area, difficult to disrupt, diverse nonspace
PNT service (GPS-Earth/eLoran)
• Develop standards for seamless use with space-based PNT.
• Encourage development of numerous, complementary terrestrial PNT services
to increase resilience (integrated radar, local positioning systems, inertial, etc.)
* Adapted from presentations and positions advocated by Dr. Brad
Parkinson and discussed at the US government’s Position, Navigation
and Timing Advisory Board. The Resilient Navigation and Timing
Foundation heartily supports these policies and initiatives.
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